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MODERN    ENGINES 

AND 

POWER    GENERATORS 


MODERN  ENGINES 

AND 

POWER  GENERATORS 


A  PRACTICAL  WORK  ON  PRIME  MOVERS 


AND     ^HE     ^RANSMISSION  OF  POWER 


STEAM,  ELECTRIC,  WATER,  AND  HOT  AIR 


BY 

RANKIN    KENNEDY,    C.E. 

AUTHOR  OF 

;  ELECTRICAL  INSTALLATIONS  "   "  ELECTRICAL  DISTRIBUTION  BY  ALTERNATING  CURRENTS  AND 

TRANSFORMERS"    "PHOTOGRAPHIC   AND   OPTICAL    ELECTRIC    LAMPS"   AND    NUMEROUS 

SCIENTIFIC  ARTICLES  AND  PAPERS  ON  MECHANICAL  AND  ELECTRICAL  ENGINEERING 


WITH    MANY    HUNDRED    ILLUSTRATIONS 


VOL    I. 


LONDON  : 
THE    CAXTON    PUBLISHING    COMPANY 


UNIVERSITY  ex    JALIFORNIA 

DAVIS 


PREFACE    TO    VOLUME    I 


THE  term  Modern  Engines  applies  not  only  to  engines  of  modern  design,  or  invented 
in  recent  years,  but  also  to  all  engines  found  to  serve  useful  and  efficient  purposes  at 
this  date.  Many  old  devices  and  designs  have  survived,  and  are  worthy  of  a  place  when 
presented  in  their  more  modern  developments. 

The  most  highly  developed  machinery  cannot  in  every  case  be  employed  by  the 
engineer.  In  many  instances  rough  and  ready  methods  are  necessary,  and  efficiency 
is  sacrificed  for  the  sake  of  convenience  and  simplicity.  He  has  often  to  make  use  of 
what  materials  can  be  most  readily  found  in  his  neighbourhood,  and  while  a  triple- 
expansion  steam  engine  and  a  multitubular  boiler  would  be  highly  appreciated  and  very 
economical  as  a  prime  mover,  such  an  outfit  would  be  in  many  cases  impossible  where 
less  complicated  and  more  primitive  machinery  would  be  quite  successful.  References 
are  therefore  made  to  older  types  still  in  practical  use. 

Each  Volume  of  this  work  will  contain  some  special  feature.  This  First  Volume 
discusses  the  fluid  pressure  machines  operated  by  fluid  impulse,  by  air,  water,  and 
steam  flowing  under  a  difference  of  pressure.  These  include  that  most  important  prime 
mover,  the  steam  turbine,  which  therefore  forms  the  special  feature  of  Volume  I.  Being 
a  new  subject,  and  of  great  interests  involved,  the  prior  patents  covering  the  funda- 
mental inventions  have  been  briefly  noticed,  as  well  as  all  the  more  recent  inventions 
worthy  of  notice  on  this  subject. 

The  application  of  the  steam  turbine  to  marine  propulsion  will  be  further  discussed 
later  on  in  this  work  under  "  Marine  Engines." 

The  windmill  is  worthy  of  attention  in  connection  with  the  possibility  of  trans- 
mitting and  storing  the  energy  generated.  Combined  with  storage,  the  best  site  for 
the  mill  may  be  chosen,  and  the  energy  delivered  where  required  at  any  reasonable 
distance. 

The  water  turbines  selected  for  description  are  the  latest  of  their  types,  with  special 
reference  to  governing.  Injectors  and  centrifugal  pumps  are  shortly  discussed.  These, 
although  not  prime  movers,  are  important  impulse  machines  closely  connected  with 
prime  movers  operating  by  momentum  and  fluid  velocities. 

With  a  description  of  the  best  rotary  piston  engines  which  have  hitherto  been  made, 
this  Volume  concludes  the  survey  of  the  more  elementary  prime  movers  and  their 
accessories. 

The  next  Volume  will  contain  a  full  treatment  of  internal  combustion  engines — gas 
and  oil,  also  of  hot  air  and  furnace  gas  engines  ;  motor  car  engines  and  locomotive 
engines  will  follow. 

RANKIN  KENNEDY. 


CHAPTER   I 

PAGE 

INTRODUCTORY  ........  i 


CHAPTER   II 

CLASSIFICATION  OF  PRIME  MOVERS.             ......  8 

WINDMILLS    ..........  9 

HYDRAULIC  MACHINERY         ........  28 

WATER  TURBINES     .........  33 

PULSOMETERS — HYDRAULIC  RAMS     .             .             ,             .             .             .  8 1 

STEAM  JETS — INJECTORS        ........  86 

WATER  JET  PROPELLER         ........  104 

CENTRIFUGAL  PUMPS  .  .  .  .  .  .  .  .no 

CHAPTER   III 

STEAM  TURBINES       .  .  .  .  .  .  .  .  .123 

GAS  TURBINES  .........         190 

DESIGNING  OF  STEAM  TURBINES       .  .  .  .  .  .  .193 

CHAPTER   IV 
ROTARY  PISTON  ENGINES  .  ....         200 


LIST    OF    PLATES 


TURBINE  AIR  PROPELLER  .....      Frontispiece 

PLATE     I.  GUNTHER'S  TWIN  VORTEX  TURBINES      .             .             .            Facing  page  32 

,,      II.  HYDRO-ELECTRICAL  PLANT,  WITH  SENSITIVE  GOVERNOR           .          ,,          66 

,,    III.  JET  IMPULSE  TURBINE     ......,,          78 

,,     IV.  CENTRIFUGAL  PUMP  AND  TURBINE  COMBINED    .             .                       ,,          96 

,,      V.  STEAM  TURBINE  CENTRIFUGAL  PUMPS  IN  SERIES           .             .          ,,        128 

,,     VI.  SMALL  DE  LAVAL  TURBINE  MOTOR       .             .             .             .          ,,        144 

,,  VII.  PARSONS'  TURBO  ALTERNATOR  .             .             .             .                      ,,        176 


MODERN  ENGINES  AND  POWER 
GENERATORS 


CHAPTER    I 

INTRODUCTORY 

THE  heat  engine  has  been  the  theme  of  many  great  treatises.  Like  most  other 
scientific  subjects,  it  is  easier  to  theorise  and  pursue  mathematical  investigation  on 
assumed  conditions  than  it  is  to  invent,  improve,  design,  and  construct  working  engines 
or  other  practical  appliances.  While  theories  and  mathematical  conclusions  are  valuable 
guides,  the  results  of  actual  machinery  in  practical  tests  are  of  immensely  greater  value, 
so  that,  while  giving  due  weight  to  the  theoretical  side  of  the  question,  we  shall  devote 
this  work  principally  to  inventions,  improvements,  designs,  and  constructions  in  prime 
movers. 

We  know  only  two  types  of  prime  movers  —  the  heat  engine  and  the  electric 
engine.  Windmills  and  water  wheels  derive  their  energy  primarily  from  the  heat  of 
the  sun.  Steam,  oil,  and  gas  engines  derive  their  energy  from  fuel  heat ;  they  are  all 
heat  engines. 

The  electric  engine  has  yet  to  be  made  practicable.  The  only  direct  source  of 
electrical  energy  is  the  Voltaic  battery,  and  that  supplies  only  a  small  quantity  at 
immense  expense.  All  the  electric  motors  so  much  in  use  are  driven  by  heat  engines  ; 
they  are  at  present  only  transmitters  of  the  power  or  energy  of  heat  engines.  By  their 
aid,  however,  we  are  enabled  to  accomplish  work  with  the  heat  engines  which  cannot 
be  done  by  any  other  means.  The  simplest  and  earliest  heat  engines  were  driven  by 
wind  and  water,  and  these  have  again  been  made  more  useful  by  the  electric  motor, 
transmitting  their  power  to  more  convenient  places  where  it  can  be  better  used. 

Within  recent  times  considerable  advances  have  been  made  in  prime  movers  ;  the 
dreams  of  early  inventors  have  been  realised  in  the  steam  turbine,  the  rotary  steam 
engine,  the  gas  engine,  the  oil  engine,  and  motor  car  engines.  Power  from  heat  engines 
transmitted  electrically  to  electric  motors  has  also  revolutionised  the  problems  of  rapid 
transit  on  street  railways,  underground  railways,  and  is  at  present  forcing  the  attention 
of  main  line  railways. 

The  education  of  modern  engineers  also  attracts  much  attention.  By  this  is  not 
merely  meant  the  preparation  of  youths  who  intend  to  adopt  engineering  as  a  profession 
VOL.  i. — i 


Modern  Engines 


or  trade,  but  the  education  of  the  more  important  class — the  owners,  controllers,  and 
employers  in  engineering  works.  The  staff  of  a  concern  may  be  ever  so  well  educated 
and  skilled  without  much  progress  being  made  if  the  controlling  head  is  not  keenly  alive 
to  improvements  and  new  inventions.  There  is  need  for  more  alacrity  in  adopting  new 
and  improved  methods  a'nd  machinery,  which  may  be  due  to  want  of  knowledge  regarding 
them.  There  is  no  standing  still  in  scientific  manufactures  at  this  date. 

No  employers  or  controllers  can  calculate,  like  their  forefathers,  upon  making  certain 
articles  without  improvements  for  a  long  lifetime  ;  for  good  or  ill  those  days  are  gone. 
To  illustrate  the  meaning  of  these  remarks  two  instances  in  the  author's  intimate 
knowledge  may  be  quoted — first,  the  now  highly  successful  electric  tramways  in  our 
cities  have  been,  90  per  cent,  of  them,  equipped  by  American  engineers  with 
American  machinery.  Yet  there  is  nothing  in  the  equipment  which  can  be  said  to  have 
originated  in  America.  The  overhead  trolley,  the  electromotor,  the  controller,  the 
dynamo,  and  all  the  special  electrical  apparatus  were  well  known  to  every  electrician 
about  twenty  years  ago  in  Great  Britain,  and  it  is  quite  safe  to  say  that  a  score  of  skilled 
electrical  engineers  in  Britain  could  have  been  found  in  the  year  1888,  any  one  of  whom 
could  have  designed  and  laid  out  an  electric  tramway — dynamos,  motors,  trolleys,  and 
all.  There  was  no  lack  of  education  and  skill  among  the  youths  nor  among  experts, 
but  no  employers  or  controllers  with  manufacturing  facilities  and  capital  could  be  found 
to  take  up  what  has  been  a  very  lucrative  business  to  the  Americans.  The  Americans 
have  followed  up  their  success  by  establishing  large  factories  in  England,  so  as  to  retain 
their  hold  upon  the  tramway  and  railway  electric  business. 

Take  also  letterpress  printing  machinery  :  the  largest  newspapers,  and  some  smaller 
ones,  are  all  printed  on  American  presses.  A  new  printing  establishment  putting  in  new 
machinery  nowadays  must  have  the  quickest  and  best  working  presses,  machines  with 
continuous  revolving  cylinders  and  two  revolution  or  perfector  machines.  Three  large 
press  manufacturers  in  America  have  been  shipping  these  improved  presses  in  quantity 
to  our  printing  establishments,  simply  because  the  home  manufacturers  go  on  making 
presses  without  improvements,  and  not  at  all  for  any  lack  of  skill  and  knowledge  in  the 
younger  generation  of  engineers. 

Whatever  may  be  the  cause  of  it,  there  can  be  no  doubt  that  the  class  to  whom 
we  must  look  for  the  encouragement  of  the  advances  in  practical  engineering  require 
educating,  in  some  way  or  another,  to  open  their  eyes  to  the  value  of  promptly  seizing 
upon  every  opportunity  for  securing  improvements.  It  is  very  well  for  a  country  to 
have  the  honour  and  glory  as  the  birthplace  of  improvements,  but  it  is  better,  very  much, 
if  its  captains  of  industry  take  advantage  of  them  in  time  to  advance  the  trade  and 
industry  of  the  country  before  outsiders  step  in. 

It  may  be  said  that  capitalists  and  captains  of  industry  can  avail  themselves  of 
expert  advice  ;  that,  however,  while  the  best  course  to  take  in  ordinary  matters,  is 
not  successful  in  questions  regarding  the  adoption  of  new  methods  or  manufactures. 
The  expert  desires  to  be,  above  all  things,  a  "safe  man,"  and  naturally  is  conservative 
and  timid  when  faced  with  responsibilities  involved  in  new  departures. 

If  every  speculator  consulted  the  family  lawyer  on  the  question  of  his  investments 
there  would  be  no  enterprise  in  this  world,  no  risks,  no  new  departures.  It  is  the 
robust,  acute  man,  with  a  clear  mind  and  depending  upon  his  own  education  and 
knowledge,  who  sees  and  grasps  the  possibilities  of  a  step  in  advance  ;  and  we  want 
some  powerful  stimulant  to  arouse  a  class  of  capitalists  and  controllers  in  this  country 
to  bring  out  the  best  that  is  in  the  people  for  their  own  good,  instead  of  supinely 
allowing  foreigners  to  run  away  with  all  the  inventions  and  improvements. 

Fiscal  arrangements  are  powerless  in  these  matters :  a  bolstered-up,  pampered 
industry  makes  no  progress  ;  it  does  not  require  to  progress  ;  nothing  but  energetic 
educated  enterprising  business  can  affect  the  situation.  Writings  have  often  proved 
of  value  in  directing-  movements,  especially  in  scientific  work  ;  to  some  extent  this 


Historical  3 

work  will  present  a  re'sume'  of  up-to-date  improvements,  some  already  developed,  others 
awaiting  development.  All  this  is  somewhat  of  a  digression  ;  the  excuse  for  it  is  that 
mechanical  and  electrical  sciences  are  in  their  practical  application  retarded  or  accelerated 
largely  by  the  enterprise  of  the  capitalists.  And  it  is  hoped  the  treatment  of  the  subject 
in  these  volumes  may  help  to  enlighten  many  who  would  bring  up  their  knowledge  to 
present  date. 

With  the  advent  of  the  modern  steam  turbine  the  steam  engine  has  arrived  at  its 
meridian  ;  and  the  new  Hult  rotary  engine  may  also  give  another  finishing  touch  to  the 
great  edifice  of  improvements  on  steam  engines.  These  two  departures  are  worthy  of 
the  closest  attention.  But  other  agents  besides  steam  are  calling  for  recognition. 
The  internal  combustion  engine  in  its  many  forms  has  reached  a  stage  where  it  will 
also  offer  itself  as  a  powerful  competitor  with  steam. 

Then  the  electrical  transmission  of  power  has  brought  the  great  water  powers  of 
the  world  down  from  their  inaccessible  fastnesses  in  the  mountains  to  the  workshops 
on  the  plains.  It  is  no  wild  dream,  but  quite  within  the  range  of  practical  engineering, 
to  say  that  we  could  transmit  the  energy  of  Norwegian  waterfalls  by  submarine  cables 
to  Edinburgh  to  light  the  city  and  run  its  tramways.  The  utilisation  of  our  own 
Highland  lochs  and  waterfalls  will  come  before  that  scheme. 

A  brief  sketch  of  the  history  of  the  subject  may  precede  the  description  of  prime 
movers.  It  is  proposed  to  describe  the  prime  movers  in  their  order  first,  and  then  to 
treat  details  afterwards.  That  the  ancients  became  acquainted  with  means  for  moving 
huge  masses  to  great  heights  and  over  long  distances  we  have  ample  proof  in  the 
pyramids  and  ancient  ruins.  All  primitive  machinery  was  at  first  moved  by  animal 
and  human  power,  using  the  machinery  of  levers,  wedges,  inclined  planes,  rollers, 
ropes,  and  other  early  inventions.  With  these  engines  man  early  discovered  that  if  a 
weight  of  material  could  be  moved  at  all,  however  small  a  distance  in  a  day,  he  could 
move  it  any  distance  given  plenty  of  time ;  and  that,  no  doubt,  is  the  explanation  of 
the  vast  works  carried  out  by  such  simple  engines.  Time  was  of  no  value  ;  a  few 
generations  of  men  spent  on  a  great  work  was  taken  then  as  a  matter  of  course. 

Wind  power  was  no  doubt  first  observed  on  boats  upon  the  waters.  The  wind 
would  move  a  boat  without  a  sail,  and  this  would  naturally  suggest  a  sail  to  increase 
the  effect,  and  from  a  sail  on  a  boat  to  a  sail  on  a  windmill  of  the  old  type  is  an  easy 
transition.  Water  power  was  very  early  used  to  assist  man  in  his  efforts  to  move 
things.  The  Chinese  records  prove  that  water  power  wheels  were  invented  by  them 
long  before  the  Christian  era. 

In  ancient  times  intellectual  contemplation  and  philosophical  speculations  were 
considered  dignified  and  worthy  of  the  most  active  and  learned  minds,  while  practical 
inventions  and  arts  were  considered  as  unworthy  of  notice  in  the  ancient  biographies 
and  histories,  and  during  the  dark  Middle  Ages  practical  engineering  and  science  were 
strangled  by  superstition  and  false  religion.  Galileo  had  to  deny  the  motion  of  the 
earth  round  the  sun  to  save  his  life.  Owing  to  these  prejudicial  effects  we  cannot 
trace  the  earliest  beginnings  of  prime  movers  ;  even  the  steam  engine  may  have  been 
invented  long  before  any  record  we  can  trace. 

The  supposed  higher  dignity  of  mental  contemplation  and  philosophical  speculation 
still  exists  to  some  extent  in  ancient  universities,  but  from  the  time  of  the  sixteenth 
century  the  progress  of  mechanical  invention,  scientific  discovery,  and  application  to  the 
work  of  the  world  has  been  very  rapid  and  wonderful. 

Heat  engines  are  first  found  mentioned  in  Hero's  Pneumatics,  written  130  B.C.,  in  which 
he  describes  a  steam  turbine  of  quite  a  practicable  design,  and  also  a  steam  pump  for 
water  raising.  Another  work,  published  in  1601,  on  pneumatics,  by  Battista  della 
Porta,  describes  a  steam  water  pump  much  the  same  as  Hero's,  but  working  with 
a  vacuum  to  raise  the  water  into  a  receiver,  from  which  it  was  expelled  by  steam. 

In  1629  Branca  described  and  operated  a  steam  turbine  in  which  a  steam  jet  drove 


Modern  Engines 


a  wheel  with  vanes.  He  managed  to  explode  his  steam  boiler,  and  was  shut  up  as 
a  prisoner  on  the  plea  that  he  must  be  mad.  In  England  the  Marquis  of  Worcester 
set  up  and  worked  a  steam  pump  at  Vauxhall  in  1656.  In  1697  Savery  improved 
Worcester's  pump,  and  it  was  introduced  and  much  used  for  mine  drainage.  This 
seventeenth  century,  therefore,  proved  one  in  which  the  steam  engine  inventors  were 
allowed  to  make  known  and  use  their  engines  ;  but  so  far  these  engines  were  steam 
turbines  or  water  pumps,  in  which  the  steam  pressure  acted  directly  on  the  water  and 
forced  it  up. 

The  next  step  in  the  evolution  of  the  heat  engine  was  one  which  was  bound  to  come 
as  better  mechanical  construction  advanced.  As  soon  as  mechanics  became  capable  of 
forming  cylinders,  rods,  plates,  and  other  pieces  of  metal  with  some  accuracy  of  shape 
and  form,  it  became  possible  to  advance  the  heat  engine.  In  1690  Denis  Papin  had 
succeeded  in  constructing  a  cylinder  and  piston,  the  prototype  of  all  our  powerful  steam 
engines  up  to  within  ten  years  ago. 

He  made  a  cylinder  and  fitted  a  piston  into  it,  and  in  the  lower  part  of  the  cylinder 
he  placed  some  water  ;  on  placing  the  cylinder  on  a  fire  the  steam  produced  forced  up 
the  piston,  on  swinging  the  cylinder  from  off  the  fire  the  steam  condensed  and  the  piston 
was  forced  down  again.  Here  we  have  the  elements  of  the  reciprocating  steam  engine. 
And  Papin,  true  to  the  inventor's  instincts,  enthusiastically  describes  his  dreams  of 
steam  pumps,  and,  by  rack  and  pinion,  turning  wheels  and  driving  paddles  on  ships,  all 
of  which  were  quite  feasible  in  his  mind,  but  far  beyond  the  skill  of  the  mechanics  of  his 
day  to  put  into  practice. 

It  is  to  this  day  even  a  remarkable  fact  that  inventors  are  sometimes  ahead  of  the 
practical  mechanic.  Many  an  inventor  conceives  a  valuable  improvement,  works  it  out 
in  his  own  mind,  and  finds  that  the  resources  of  the  constructors  and  mechanics  are  not 
sufficient  to  realise  his  schemes. 

All  the  early  steam  turbine  inventors  were  baffled  in  their  attempts,  simply  for  want 
of  tools  and  machinery  sufficiently  good  to  make  their  turbines.  The  recent  success  of 
the  steam  turbine  has  been  more  due  to  the  refinement  of  modern  machine  tools  and 
accuracy  of  metal-working  machinery  than  to  any  new  principles  or  inventions. 

Nowadays  the  inventor  has  many  advantages  denied  to  the  old  pioneers, — machine 
tools  are  now  made  to  produce  almost  anything  in  metal  with  the  utmost  precision, 
however  complicated.  A  piston  and  cylinder  are  now  fitted  to  the  y^Vry  °f  an  inch  easily, 
while  James  Watt  was  delighted  when  he  succeeded  in  getting  a  fit  so  close  that  he 
could  not  slip  a  half-crown  between  the  piston  and  cylinder. 

Papin  invented  also  a  safety  valve  for  his  boiler,  and  so  escaped  the  misfortunes  of 
poor  Branca. 

Then  followed  Savery,  Newcomen,  and  Cawley,  who  combined  the  separate  boiler, 
cylinder,  and  piston  with  condensing  water  injected  into  the  cylinder.  Potter  added  the 
self-acting  valves ;  Leupold  and  Smeaton  added  improvements,  so  that  at  the  end  of 
the  seventeenth  century  the  steam  engine  had  become  a  well-known  useful  machine. 
Although  frightfully  inefficient,  it  had  plenty  of  power,  and  did  good  work. 

James  Watt  took  up  the  question  in  1759,  and  ten  years  after  filed  the  most 
important  patent  specification  the  world  ever  saw,  describing  his  improvements  in  steam 
engines.  And  after  all,  it  was  to  Scotland  and  a  Scotchman  we  are  indebted  for  the 
final  solution  of  the  steam  reciprocating  engine  problems  ;  aided,  however,  by  Matthew 
Boulton's  financial  assistance  and  personal  energy,  without  which  it  must  be  admitted 
that  James  Watt's  great  genius  would  have  been  lost.  Dr.  Roebuck,  of  Carron  Iron 
Works,  had  helped  Watt  at  the  outset,  and  enabled  him  to  make  a  start.  Boulton  was 
a  discoverer,  and  his  greatest  discoveries  were  James  Watt,  and  later  on  Murdoch, 
the  inventor  of  coal  gas  lighting.  Matthew  Boulton  and  James  Watt  carried  out  their 
great  engineering  work  in  Birmingham,  and  they  had  a  long  and  bitter  fight  in  the  law 
courts  to  maintain  their  rights  to  Watt's  inventions. 


Historical 


The  chief  claims  of  Watt's  patent  of  1769  are  worth  recording1  here.  In  Watt's  own 
words — 

"  First,  That  vessel  in  which  the  powers  of  steam  are  to  be  employed  to  work  the 
engines,  which  is  called  the  cylinder  in  common  fire  engines,  and  which  I  call  the  steam 
vessel,  must,  during-  the  whole  time  the  engine  is  at  work,  be  kept  as  hot  as  the  steam 
that  enters  it ;  first,  by  enclosing  it  in  a  case  of  wood,  or  any  other  materials  that 
transmit  heat  slowly  ;  secondly,  by  surrounding  it  with  steam  or  other  heated  bodies  ; 
and  thirdly,  by  suffering  neither  water  nor  any  other  substance  colder  than  the  steam  to 
enter  or  touch  it  during  that  time. 

"Secondly,  In  engines  that  are  to  be  worked  wholly  or  partially  by  condensation 
of  steam,  the  steam  is  to  be  condensed  in  vessels  distinct  from  the  steam  vessels  or 
cylinders,  although  occasionally  communicating  with  them  ;  these  vessels  I  call  con- 
densers ;  and,  whilst  the  engines  are  working,  these  condensers  ought  at  least  to  be 
kept  as  cold  as  the  air  in  the  neighbourhood  of  the  engines,  by  application  of  water,  or 
other  cold  bodies. 

"Thirdly,  Whatever  air  or  other  elastic  vapour  is  not  condensed  by  the  cold  of  the 
condenser,  and  may  impede  the  working  of  the  engine,  is  to  be  drawn  out  of  the  steam 
vessels  or  condensers  by  means  of  pumps  wrought  by  the  engines  themselves,  or 
otherwise. 

"  Fourthly,  I  intend,  in  many  cases,  to  employ  the  expansive  force  of  steam  to  press 
on  the  pistons,  or  whatever  may  be  used  instead  of  them,  in  the  same  manner  in  which 
the  pressure  of  the  atmosphere  is  now  employed  in  common  fire  engines.  In  cases 
where  cold  water  cannot  be  had  in  plenty,  the  engines  may  be  wrought  by  this  force  of 
steam  only,  by  discharging  the  steam  into  the  air  after  it  has  done  its  office. 

"  Lastly,  Instead  of  using  water  to  render  the  pistons  and  other  parts  of  the  engines 
air  and  steam  tight,  I  employ  oils,  wax,  resinous  bodies,  fat  of  animals,  quicksilver,  and 
other  metals  in  their  fluid  state." 

Watt  afterwards  proceeded  to  detail  inventions, — the  pendulum  engine  governor, 
the  engine  power  indicator,  the  parallel  motion,  the  expansive  working  by  cut-off  at  a 
fraction  of  the  piston  stroke,  the  double  acting  engine,  the  butterfly  valve,  and  other 
inventions,  brought  the  engine  to  great  perfection.  It  may  seem  strange  that  such  a 
simple  thing  as  a  crank  for  converting  reciprocating  to  rotary  motion  was  unknown 
in  Watt's  time,  yet  it  seems  it  was  not  known  then,  for  it  was  invented  by  Watt,  but 
pirated  and  patented  by  another. 

When  one  considers  that  only  a  little  more  than  one  hundred  years  ago  a  crank  and 
connecting  rod  and  fly-wheel  were  new  things,  the  extraordinary  progress  made  between 
1785  and  1885  can  be  realised. 

It  is  of  little  interest  to  follow  the  history  of  the  steam  engine  after  Watt's  time  ;  all 
subsequent  improvements  have  been  mere  details,  and  more  due  to  taking  advantage 
of  improved  materials  and  machine  tools  for  better  construction,  using  higher  pressure, 
greater  expansion,  and  multiple  cylinders. 

The  reciprocating  engine  has  reached  its  zenith  in  our  day,  and  will  likely  hold  the 
first  place  in  many  uses  for  many  years  to  come,  but  the  march  of  improvement  never 
ceases.  The  steam  turbine,  so  long  impossible  for  want  of  means  to  properly  construct  it, 
has  at  last  been  evolved,  and  is  now  beginning  to  compete  successfully  with  the  Watt 
engine,  which  it  is  destined  to  supersede  altogether  in  the  steam-engine  world.  The 
rotary  steam  engine  has  been  the  dream  of  every  engineer  ;  even  Watt  spent  much  time 
upon  it,  but  it  has  hitherto  baffled  all  inventors.  Recently,  however,  a  new  rotary  engine 
has  been  constructed  which  in  an  exceedingly  beautiful  and  simple  manner  overcomes  the 
chief  difficulty,  that  is,  the  internal  friction  of  the  revolving  piston,  so  that  hopes  are 
raised  also  in  this  direction. 

Steam,  however,  has  its  limitations,  now  well  defined  by  scientists,  and  the  point 
seems  almost  to  be  reached  beyond  which  nature  puts  a  stop  to  further  improvement. 


Modern  Engines 


This  is  not  to  be  wondered  at,  for  during-  one  hundred  and  fifty  years  the  steam  engine 
and  its  details  have  been  the  subject  of  tens  of  thousands  of  improvements  and  patents, 
and  the  research  of  physicists  of  the  highest  ability,  mathematicians,  mechanicians,  and 
experts  on  steam. 

Another  type  of  heat  engine  was  early  proposed,  and  has  been  the  subject  of  much 
study,  namely,  the  "internal  combustion  engine."  This  title  includes  all  that  large  class 
of  engines  in  which  the  working  fluid  is  hot  air,  heated  in  the  cylinder  by  combustion 
with  gas,  or  gasified  oils,  or  fuel  dust. 

The  fuel  being  burned  in  the  cylinder  direct,  the  efficiency  should  be  higher  than  that 
of  the  steam  engine,  and  it  is  so  ;  but  the  high  efficiency  which  might  be  expected  has 
not  yet  been  reached,  a  good  deal  of  room  for  improvement  still  exists  in  these  hot  air 
internal  combustion  engines.  High  piston  speed  should  be  aimed  at,  and  proper  balanc- 
ing and  cushioning-  of  the  reciprocating  parts  should  receive  more  attention. 

The  simple  external  combustion  hot  air  engine  has  a  small  field  of  usefulness,  but  is 
of  no  account  for  large  powers. 

The  designs  of  engines,  steam,  gas,  oil,  and  hot  air,  are  very  numerous  ;  adopted  to 
many  various  purposes,  we  shall  only  study  the  modern  types,  leaving  out  the  old  beam, 
oscillating,  grasshopper,  side-lever,  steeple,  and  other  obsolete  types,  most  of  these 
designs  being  made  to  suit  the  tools  of  the  builder.  Thus  if  an  engine  maker  had  no 
large  planing  machine  for  iron  slides,  he  designed  the  engines  to  be  made  without  planed 
slides.  Turning  and  boring  tools  preceded  shaping  and  planing  tools,  hence  old 
engines  were  designed  with  an  eye  to  do  all  the  machined  work  for  them  in  the  lathe, 
and  all  the  motion  gear  in  the  forge  or  smithy. 

The  other  source  of  energy,  electricity,  has  become  of  great  importance  as  a 
secondary  power.  Electricity  cannot  yet  be  liberated  from  fuel,  like  heat,  by  simple 
combustion.  The  Voltaic  battery  is  the  only  available  source  of  electricity  direct  from 
fuel,  and  as  it  uses  expensive  fuel  with  much  waste  it  is  not  of  commercial  importance  for 
power  purposes.  But  by  converting  the  power  of  a  heat  engine  into  electrical  energy 
we  obtain  the  most  economical  and  ready  means  for  transmitting  energy  for  power  and 
light.  For  this  purpose  it  is  only  necessary  to  attach  a  dynamo-electric  machine  to  be 
driven  by  the  heat  engine. 

As  a  secondary  power,  electricity  has  a  great  field  of  usefulness.  It  also  converts 
the  heat  engine  power  into  a  force  which  can  be  applied  to  chemical  and  metallurgical 
purposes  in  producing  aluminium  and  refining  copper.  The  production  of  caustic  soda, 
potass,  and  carbide  of  lime,  nitric  acid,  carborundum,  potass  chloride,  and  many  other 
processes  are  capable  of  being  carried  out  electrically. 

As  a  secondary  engine,  the  compressed  air  engine  is  also  of  much  use,  especially  for 
drilling,  riveting,  and  caulking  in  boiler  and  shipbuilding  work.  Also  in  rock-drilling 
in  mines  we  shall  have  occasion  to  consider  compressed  air  engines  very  fully. 

In  the  case  of  the  internal  combustion  engines,  we  have  in  the  oil  engine  a  complete 
power  generator,  in  itself  requiring  no  separate  gas  or  other  generator ;  hence  its 
extremely  suitable  application  to  motor  cars. 

But  gas  engines  require  gas  generators.  These  are  of  much  interest  to  engineers,  as 
offering  a  means  of  producing  gas  for  power  purposes  from  cheap  fuel  by  a  simple  and 
cheap  process. 

The  steam  boiler  is  a  necessary  part  of  the  steam  plant,  and  has  received  almost  as 
much  attention  as  the  engine  ;  in  its  many  forms  adapted  to  many  different  purposes 
we  have  a  large  subject  to  study  of  very  great  interest.  The  fuels  available  for 
producing  heat  are  not  many, — coal,  wood,  oil,  natural  gas,  waste  products  such  as 
straw,  cane,  sawdust,  and  dust  destructors.  To  coal  the  British  Isles  are  indebted  for 
their  huge  manufacturing  industry ;  it  has  been  cheap  and  plentiful,  giving  about 
14,000  B.  th.  units  per  Ib.  burned.  When  coal  becomes  scarce,  or  is  at  last  all  used 
up  in  these  islands,  a  vast  change  in  the  industrial  world  must  have  occurred.  Coal  is 


Introductory 


being-  used  up  at  an  enormous  rate,  which  goes  on  increasing-  yearly.  The  only  hope 
is  that  engineers  will  soon  discover  an  engine  in  which  coal  can  be  more  economically 
used  ;  the  best  heat  engines  are  at  present  very  wasteful  of  fuel,  the  steam  engine 
wasting  about  80  per  cent,  of  its  fuel  at  this  present  day.  What  a  field  for  invention 
and  improvement  this  fact  discloses  ! 

In  many  manufacturing  processes  fuel  is  also  recklessly  wasted  to  a  large  extent. 
In  the  iron-blast  furnaces  coal  consumption  has  been  gradually  reduced,  and  the 
utilisation  of  the  furnace  gases  for  power  purposes  promises  a  further  saving.  Coke  is 
used  for  many  purposes,  and,  as  at  present  made,  all  the  gaseous  and  liquid  products 
are  wasted  in  its  manufacture  ;  the  blazing  coke  heaps  and  coke  ovens  are  a  terrible 
waste  of  fuel.  The  prodigal  abuse  of  Nature's  greatest  store  of  energy  on  earth  is 
pitiful.  Coal  can  never  be  restored  in  the  ages  of  man,  and  a  coalless  country  can  never 
be  anything  but  a  thinly  populated  agricultural  and  pastoral  land.  The  saving  of  coal 
is  one  of  the  engineer's  chiefest  problems.  Mineral  oil  has  been  found  plentiful  in  some 
localities  in  Russia  and  America,  and  can  be  made  from  Scottish  shale.  As  a  fuel,  it  is 
far  inferior  to  coal,  but  it  is  convenient  for  transhipment.  Whether  the  oil  supplies  will 
last  for  long  or  short  times  we  cannot  know.  Texas  seems  to  have  a  large  natural 
supply  of  crude  petroleum,  which,  being  of  little  use  for  anything  else,  is  sold  cheap 
for  power  purposes.  In  a  suitable  engine  it  gives  i  horse-power-hour  for  one 
farthing. 

In  colonial  countries  boilers  are  in  many  cases  fired  by  straw  and  wood,  the  furnaces 
being  constructed  specially  for  the  purpose,  as  the  fuel  is  very  bulky  compared  with 
its  output  of  heat.  At  timber  works,  saw  mills,  etc.  the  waste  wood  and  sawdust  is 
used  for  fuel  to  work  the  engines. 

The  refuse  destructor  in  large  towns  and  cities  produces  heat  sufficient  for  raising 
a  large  quantity  of  steam,  which  in  some  cases  is  used  for  electric  lighting  purposes. 

In  tropical  countries  direct  sun  heat  has  been  used  for  raising  steam  for  small 
engines,  the  boiler  being  placed  in  the  focus  of  a  large  mirror. 

All  these  fuels  and  their  uses  are  well  worthy  of  the  engineer's  attention  ;  and  the 
accumulated  knowledge  of  their  values,  and  the  best  uses  to  make  of  them,  is  to  be 
gathered  in  this  work  in  later  chapters. 

Condensers,  economisers,  pumps,  valves,  and  all  the  many  accessories  of  modern 
prime  movers  we  will  discuss  in  their  proper  places. 


CHAPTER    II 

PRIME  MOVERS,  CLASSIFICATION  OF 

IN  treating1  this  extensive  subject  there  are  two  methods  of  procedure.  First,  to  begin 
with  the  sources  of  energy — fuel,  heat,  electricity,  and  the  elements  of  mechanism, 
thermodynamics,  electrodynamics,  fluid  pressures  ;  and  thence  to  engine  designs  and 
constructions.  This  course,  however  suitable  as  an  educational  curriculum,  is  not  of  so 
much  practical  value  as  the  second  method  ;  in  this  we  follow  more  closely  the  natural 
course  of  development  of  the  prime  mover.  Engines  were  successfully  constructed  and 
used  without  a  knowledge  of  the  exact  sciences  connected  with  their  theory  of  action, 
this  knowledge  forerunning  the  theories.  As  an  analogy,  we  may  refer  to  the  science 
of  physiography.  A  surveyor  could  possibly  by  scientific  measurements  and  observa- 
tions and  exact  calculations  delineate  on  a  map  the  approximate  course  of  a  river 
from  his  knowledge  of  the  watershed  ;  while  an  ordinary  traveller,  beginning  at  the 
mouth  of  the  river,  could  by  simple  observations  obtain  a  far  more  accurate  and  exact 
knowledge  by  following  the  course  from  mouth  to  source.  In  the  same  way  we  shall 
begin  where  the  pioneers  in  engine  making  started,  namely,  where  they  commenced 
to  make  engines  without  inquiring  closely  into  the  more  abstruse  problems.  These 
deeper  scientific  questions  follow  naturally  as  the  subject  develops.  The  fluid  pressure 
engines  are  primarily  engines  the  working  substance  in  which  are  fluids. 


CLASSES  OF  PRIME  MOVERS 
Fluids  are  of  two  kinds — liquids  and  gases. 

i.  Natural  Fluid  Pressure  Engines 

Natural  fluid  pressures  are  used  in  windmills — air  pressure ;  and  in  water  engines, 
wheels,  and  turbines — liquid  pressure. 


2.  Steam  Engines 

Artificial  fluid  pressure  engines  are  those  in  which  the  pressure  is  produced  by 
heat  from  fuel  combustion,  and  comprise  steam  and  hot  air  engines.  Steam  engines 
are  of  three  classes  : — 

(1)  Steam  turbines. 

(2)  Reciprocating  piston  engines. 

(3)  Rotary  piston  engines. 

8 


Classification 


3.  Hot  Air  Engines 

Hot  air  engines  are  of  two  kinds  : — 

(1)  External   combustion   engines,   in   which   the   fuel   is   burned   outside   the 

engine. 

(2)  Internal  combustion  engines,  in  which  the  fuel  is  burned  inside  the  engine  ; 

to  this  class  belongs  the  gas  and  oil  engines. 

4.  Electric  Engines 

In  this  class  the  energy  is  applied  by  electric  pressure  generated  from  fuel  by 
chemical  combination,  which  may  be  properly  described  as  combustion  without  heat, 
electric  pressure  being  the  result,  instead  of  high  temperature. 

5.  Secondary  Engines 

These  are  engines  operated  by  fluid  pressure  or  electric  pressure,  generated  by 
some  prime  mover  of  the  types  belonging  to  Classes  i  and  2,  such  as  compressed 
air,  turbines  driven  by  water  which  has  previously  been  pumped  up  to  a  height  by 
a  windmill,  water  turbine,  steam  or  gas  engine,  and  electromotors  driven  from  dynamos. 


WINDMILLS 

The  windmill  and  water  wheel  naturally  preceded  the  heat  engine  in  practice.  We 
therefore  begin  with  these  engines,  and  will  follow  in  the  order  here  given,  with  the 
consideration  of  the  construction  of  the  others. 

Naturally,  wind  power  would  be  the  earliest,  and  windmills  the  first  prime  movers. 
The  force  of  the  wind  is  self-evident,  and  the  first  attempts  to  utilise  it  were  no  doubt 
in  the  direction  of  propelling  boats  by  sails.  At  the  present  day  sails  and  masts  are 
still  used  on  large  vessels  for  propulsion.  The  sailing  vessel  can  be  moved  in  opposite 
directions  by  the  same  wind,  and  can  sail  on  a  course  at  an  angle  in  part  against  the 
wind.  This  feat  would  at  first  be  found  by  experiment ;  but  it  can  be  demonstrated 
by  the  principle  of  the  resolution  of  forces  as  given  in  text-books  on  Mechanics. 

The  old  windmills  so  conspicuous  on  the  landscape  were  mechanically  simply  four 
masts,  with  one  sail  on  each,  set  on  a  rotating  shaft.  In  a  lo-mile  breeze  a  15-foot 
wheel  gave  about  i  horse-power,  and  the  power  given  was  roughly  about  proportional 
to  the  square  of  the  diameter  from  tip  to  tip  of  the  sails,  and  the  best  results  obtained 
when  the  speed  in  feet  of  the  sail  tips  was  about  2.5  times  the  speed  of  the  wind. 

The  old  windmill  did  good  work  in  its  day,  and  its  more  scientific  successor  is 
capable  of  still  better  performances.  Far  from  regarding  the  windmill  as  a  sailing 
body  like  a  boat,  the  modern  engineer  now  considers  it  in  its  true  light  as  a  fluid 
pressure  turbine.  Like  water  power,  the  best  sites  for  the  wheel  are  generally  far 
away  from  the  points  where  the  power  is  required,  so  that  some  system  for  transmitting 
the  power  must  be  adopted  to  obtain  the  best  results.  And  again,  as  with  all  natural 
forces  beyond  the  control  of  man,  some  system  of  storage  must  be  employed  if  the 
force  is  to  be  ready  for  use  daily  at  command. 

In  electricity  we  have  both  requirements  provided — a  means  of  storage  and  a 
means  for  transmission — so  that  we  can  store  up  the  power  when  the  wind  blows  ; 
and  in  designing  the  pjant,  place  the  wheel  on  the  best  available  site,  even  miles  from 
where  the  power  is  wanted,  and  then  transmit  the  power  by  electric  current  from  the 
wheel  to  the  work  to  be  done.  This  electrical  transmission  puts  both  wind  and  water 
power  on  quite  a  different  footing  from  that  on  which  they  stood  twenty  years  ago. 
At  that  time  steam  had  carried  all  before  it,  but  since  then  it  has  been  found  that 


10 


Modern  Engines 


steam  does  not  accomplish  everything"  desired.     It  has  its  limitations,  which  are  now 
clearly  defined  ;  and  more  attention  is  paid  to  other  working-  fluids  for  prime  movers. 

Now,  when  we  can  choose  the  highest  and  most  suitable  site  for  a  windmill,  and 
transmit  the  power  any  reasonable  distance  for  use,  it  becomes  a  more  generally 
applicable  prime  mover. 

Windmills  are,  however,  very  limited  in  power.  A  pleasant  breeze  flows  about 
10  miles  per  hour ;  and  as  that  can  be  counted  upon  for  about  8  hours  a  day  on  an 
average,  it  is  taken  as  a  minimum  standard.  The  power,  however,  increases  nearly  as 
the  square  of  the  speed  of  the  wind,  so  that  the  power  varies  largely. 

In  practice  it  is  found  that  well-made  modern  mills  and  water  pumps  will  do  the 
work  as  under. 

TABLE  I. 


Diameter  of  Sail 
in  Feet. 

Water  raised  in  Gallons 
100  Feet  high  per 
Hour  with  lo-mile  Wind. 

Horse-power  in 
Work  done. 

Wind  at  20  Miles 
per  Hour 
Horse-power. 

7 

80 

*Vth 

Aths 

10 

200 

j>5th 

$ths 

12 

35° 

1th 

^ths 

16 

700 

Jrd 

ifrd 

20 

1  200 

fibs 

3 

The  above  figures  are  for  mills  driving  water  pumps  direct  without  gearing. 
Geared  mills  work  the  pumps  slower,  and  are  generally  used  where  power  is  taken 
direct  from  the  mill. 

TABLE  II. 


Diameter  of  Sail 
in  Feet. 

Water  raised  TOO 
Feet  per  Hour 
jo-mile  Wind. 

Horse-power 
approximate  with 
2O-mile  Wind. 

25 
30 
35 
40 

Gallons. 

2000 

3000 
4500 
6060 

4 
5i 
74 

12 

(Actual  Brake 
j  Horse-power. 

The  power  should  be  as  the  square  of  the  diameter  of  the  wheel  and  as  the  square 
of  the  velocity  of  the  wind.     The  horse-power  in  water  raised  in  feet  per  hour  equals 

gallons  x  i o  x  f eetjieigjit^  multiplying>  gaiiOns  by  10  to  get  Ibs.     Thus  for  a  25-foot  mill 
60x33,000 

2000  x  io  x  IPO  _  i  horse-power  ;  and  as  the  power  is  as  the  square  of  the  velocity  of 
60  x  33,000 

wind,  we  would  eet  for  a  2O-mile  wind  —  =4  horse-power  at  that  velocity. 

io'2 


USEFUL   FORMULA 

The  force  of  wind  increases  as  the  square  of  its  velocity. 

a  =  area  exposed  at  right  angles  to  the  wind  in  square  feet  ;  F  =  force  of  the  wind 
in  Ibs.;    H  =  horse-power  ;  and  v  =  velocity  of  the  plane   a  in  direction   of  the   wind, 
+  when  it  moves  opposite,  and  —  when  it  moves  with  the  wind. 
F  =  0.0022880  V2,  when  v  =  o 


F  =  o.oo2288*(V  ±vy 


H 


. 
240384.6 


Wind  Power  1 1 

Example. — A  rail  train  running  E.N.E.  25  miles  per  hour  exposes  a  surface  of 
1000  square  feet  to  a  pleasant  brisk  gale  N.E.  by  N.  Required  the  resistance  to  the 
train  in  the  direction,  it  moves  and  the  horse-power  lost. 

E.N.E. -N.E.  by  N.  =  3  points  =  33°  45';  V  =  14  feet  per  second,  a  brisk  gale; 
v=  25  x  1.467  =  36.6  feet  per  second;  and  F  =  o.oo2288  sin.  33°  45' x  1000  (i4  +  cos. 
33°  45' x  36.6)2  =  305.  i  Ibs. 

TT       ^O^.I  X  76.6 

H  =  ^-^ a —  =  20  horses. 

550 

The  motions  and  effects  of  gases  by  the  force  of  gravity  are  analogous  to  those  of 
liquids. 

The  altitude  or  head  of  the  atmosphere  at  uniform  density  will  be  the  altitude  of  a 
column  of  water  33.95  feet  divided  by  the  specific  gravity  of  the  air,  0.0012046,  or 

33'95     =28, 183  feet. 
0.0012046 

The  velocity  due  to  this  head  will  be  V  =  8.O2  v/28, 183  =  1346.4  feet  per  second,  the 
velocity  with  which  the  air  will  pass  into  a  vacuum. 


VELOCITY   OF   WIND 

When  air  passes  into  an  air  of  less  density,  the  velocity  of  its  passage  is  measured 
by  the  difference  of  their  density. 

H  and  h  =  density  of  the  air  in  inches  of  mercury;  /=  temperature  at  the  time  of 
passage  ;  and  V  =  velocity  of  the  wind  in  feet  per  second. 

/j_j[  _  fa 
V=  1346.4*  /  — - — (i  +0.00208^). 


As  the  wind  averages  between  10  and  20  miles  per  hour,  we  might  count  on  an 
average  between  i  and  4  horse-power  as  the  output  of  a  mill  of  25  feet  diameter  on  a 
jo-foot  tower  placed  in  a  favourable  situation.  These  observations  refer  to  the  ordinary 
modern  mill  as  shown  in  Fig.  i  ungeared,  and  in  Fig.  2  geared,  in  which  the  sails  are 
moving  in  a  plane  at  right  angles  to  the  wind,  and  are  set  at  an  angle  such  that  the 
tips  of  the  sails  move  about  2.5  times  the  velocity  of  the  wind.  Thus  the  25-foot  wheel 
would  in  a  2O-mile  wind  make  24  revolutions  per  minute,  not  an  excessive  speed. 
This  type  of  wheel  has  the  advantage  over  others  of  presenting  every  blade  constantly 
to  the  cylinder  of  wind  which  it  intercepts,  and  runs  at  a  fairly  high  speed.  The  whole 
of  the  blade  is  not  equally  effective,  however,  as  its  effect  decreases  towards  the  centre, 
where  the  wind  has  less  leverage,  and  in  high  gales  it  is  apt  to  be  damaged,  so  that 
attempts  have  been  made  to  design  other  forms,  which  we  will  also  describe. 

In  this  present  form  the  blades  are  flat  metal  sheets,  geared  so  that  they  can 
be  feathered  in  order  to  present  them  at  different  angles  to  the  wind,  in  some  cases 
to  turn  them  edge  on  in  high  gales  so  as  to  reduce  the  pressure.  This  geared  mill 
is  shown  in  Fig.  2.  The  little  windmill  at  the  back  winds  the  large  wheel  round, 
so  that  it  always  automatically  presents  the  same  face  to  the  wind.  The  blades  also 
automatically  adjust  themselves  in  heavy  winds  so  as  to  prevent  excessive  speeds. 
These  automatic  gears  are  necessary  on  all  large  mill  wheels  of  this  type.  The  small 
wheel  is  known  as  the  fantail.  In  some  old  mills  it  was  little  else  than  a  tail,  a  flat 
board  on  a  tail  rod  on  the  axis  of  the  wheel. 

Referring  to  Fig.  i,  which  illustrates  the  smaller  mills  ungeared  for  pumping  water, 
made  by  Messrs.  Robert  Warner  &  Co.,  the  mills  are  provided  with  fixed  galvanised 
vanes,  fixed  to  circular  rings  and  arranged  to  turn  partly  out  of  the  wind  when  the 
velocity  ot  the  latter  is  higher  than  is  required  for  the  proper  working  of  the  mill. 
Fantails  are  provided  to  each  mill  for  maintaining  the  sail  to  the  wind.  Suitable 
gearing  is  arranged  for  conveniently  putting  the  mill  into  or  out  of  work  from  the 


12 


Modern  Engines 


ground  level,  so  that  the  attendant  need  not  go  to  the  top  except  for  the  purposes  of 
lubricating,  which  is  very  seldom  required.  The  towers  are  made  square  (excepting  for 
the  larger  sizes,  which  would  be  hexagon),  having  four  corner  posts  of  angle  section, 
with  suitable  strong  strengthening  rings  and  bracings.  These  are  made  mainly  of 
steel,  wrought  iron  being  used  for  bolts  and  other  smaller  parts.  The  towers  are 


FIG.  i — Simple  Ungeared  Windmill. 


FIG.  2 — Geared  Windmill. 


arranged  for  bolting  down  to  four  blocks,  which  may  be  of  concrete,  brickwork,  or  other 
suitable  materials  that  may  be  available. 

The  sail  and  pump  shafts  are  of  best  steel,  the  bearings,  including  the  turntable 
and  millhead,  being  very  carefully  designed  so  as  to  give  the  smallest  amount  of  friction. 
Special  attention  is  given  to  the  parts  requiring  lubrication,  so  as  to  need  the  least 
possible  attention. 


Windmills 


The  geared  mills  are  constructed  of  larger  sizes,  from  20  to  40  feet  in  diameter.  The 
Figure  2  is  from  a  photograph  of  a  4o-foot  mill  supplied  to  the  Government  for  Egypt. 

These  mills  are  substantially  built  with  very  large  wearing  surfaces,  which  are 
well  provided  for  means  of  lubrication,  thus  rendering  them  very  durable.  They  are 
automatic  in  their  action  during  heavy  winds,  so  that  excessive  speeds  which  might 
cause  damage  are  avoided.  The  winding  gear  consists  of  a  geared  back  fantail  which 
is  far  the  most  efficient  and  satisfactory  type  to  adopt  with  geared  windmills.  They 
can  also  be  quickly  started  and  stopped  by  hand  from  ground  level.  The  power  is 
transmitted  from  the  sail  shaft  to  the  ground  or  any  other  level  of  the  tower  by  a  pair  of 
bevel  wheels  and  upright  shaft.  The  power  can  be  taken  from  the  latter  or  from  a 
horizontal  as  may  be  most  convenient.  The  towers  are  made  mainly  of  steel,  wrought 
iron  being  used  for  bolts  and  sqme  of,  the  smaller  parts.  The  smaller  towers  are 
square  and  the  larger  ones  hexagon,  all  hav- 
ing suitable  strengthening  rings  and  brac- 
ings, and  are  arranged  for  being  bolted 
down  to  suitable  foundations,  such  as  con- 
crete, brickwork,  etc. 

The  first  cost  of  windmills  is  not  high. 
A  2O-foot  mill  ungeared  with  a  3o-foot  iron  tower  costs 
about  £140,  giving  from  about  i  to  3  horse-power.  A 
4O-foot  mill  giving  from  6  to  12  horse-power,  complete 
with  a  4O-foot  tower,  costs  about  ^470.  When  we 
consider  the  simplicity  of  the  machine,  its  small  cost  for 
upkeep,  and  no  cost  whatever  for  fuel,  these  prices  are 
not  excessive. 

These  prices,  however,  do  not  include  the  cost  of  the 
power  transmitting  or  utilising  gear ;  say,  for  instance, 
the  pump,  if  it  is  for  water  raising,  is  not  included.  We 
will  return  to  this  point  after  we  have  discussed  the  other 
two  forms  of  wind  wheels. 

A  wind  wheel  which  rotates  with  its  axis  vertical 
and  the  wheel  horizontal  was  designed  by  Robinson  to 
register  the  average  speed  of  the  wind  over  a  given 
period.  This  form  of  wheel  depends  for  its  action 
upon  the  difference  of  resistance  offered  to  the  wind 
by  the  concave  and  convex  sides  of  a  hollow  hemi- 
sphere. The  convex  sides  offer  much  less  resistance, 
hence  the  wheel  revolves  in  the  direction  pointed  by  the 

convex  side.  It  is  thus  evident  that  the  whole  pressure  of  the  wind  is  not  available, 
as  the  back  pressure  on  the  convex  side  must  be  deducted  from  the  forward  pres- 
sure on  the  concave  side  ;  and  the  pressures  act  only  for  about  one  quarter  of  a 
revolution. 

On  the  other  hand,  the  speed  can  never  exceed  that  of  the  wind,  and  the  arms 
may  be  made  long  and  strong.  A  considerable  leverage  can  be  given  to  the  acting  cup. 
The  Robinson  anemometer  is  shown  in  Fig.  3,  as  made  by  Casella. 

On  this  same  principle  the  wind  wheel  of  Professor  Blyth  is  designed.  It  is 
shown  in  Fig.  4,  the  hemispherical  cups  being  replaced  by  wooden  buckets  of 
large  size  ;  the  construction  explains  itself  pretty  clearly.  The  difficulty  with  these 
wheels  is  their  great  size  required  for  comparatively  small  powers.  A  better  design 
of  the  same  type  has  been  made  in  the  form  of  a  water  wheel,  a  portion  of  which 
is  shown  in  Fig.  5,  giving  the  delineation  of  the  vanes;  and  in  Fig.  6,  where  it  is 
seen  mounted  on  a  vertical  axis  on  a  tower.  Here  again  the  torque  is  due  to  the 
difference  of  resistance  between  the  concave  and  convex  sides  of  the  vanes ;  only,  the 


FIG.  3. — Robinson  Anemometer. 


Modern  Engines 


one  partially  screens  the  other,  so  that  the  difference  is  greater  than  it  is  with  cups 
Neither  of  these  types  are  as  efficient  as  these  shown  in  Fig's,  i  and  2. 


FIG.  4.  — Blylh's  Windmill. 


tf 


FIG.  5.—  Diagram  of  Wind  Wheel  Vanes. 


FIG.  6.— Horizontal  Wind  Wheels, 


Transmission  of  Wind   Power  15 

POWER  TRANSMISSION  GEAR  FOR  WIND  WHEELS 

The  gear  from  the  wheel  shaft  itself  consists  of  a  vertical  shaft  and  bevel  wheels, 
a  pump  and  crank  to  work  the  plunger  where  simple  water  raising  is  required.  As 
a  rule,  however,  the  water  lies  low,  in  a  well  or  pond  or  river,  while  the  best  place  for 
the  wheel  is  high  up.  And  as  we  cannot  bring  the  water  up,  we  must  take  the  wheel 
down  to  the  water,  and  thus  it  becomes  less  effective.  This  difficulty  might  be  over- 
come by  transmitting  the  power  by  some  means  from  the  high  wind  wheel  down  to 
the  low  water  pump.  Ropes  and  pulleys  and  compressed  air  have  been  used  for  this 
purpose,  but  they  are  expensive  and  inefficient,  and  the  source  of  much  trouble  ;  of  the 
two,  compressed  air  is  the  best.  In  this  system  the  wind  wheel  pumps  air  under 
pressure  into  a  receiver,  generally  a  cylindrical  steel  boiler.  From  this  an  underground 
iron  pipe  connects  down  to  the  pump  placed  at  the  water  source,  the  compressed  air 
here,  by  means  of  an  air  motor  and  water  pipe  combined  (to  be  described  under  pumps), 
pumps  the  water  up  to  a  reservoir  to  the  desired  level,  from  whence  it  is  supplied  by 
gravitation  to  the  users.  For  pumping  purposes  this  is  a  satisfactory  system,  for 
both  wind  wheel  and  water  pump  can  be  placed  just  where  they  are  most  advantageous, 
and  even  more  than  one  pump  may  be  used  from  same  wind  wheel  if  several  sources  of 
water  can  be  tapped. 

For  power  purposes  the  same  arrangement  can  also  be  used  with  advantage,  and 
by  providing  large  storage  vessels  for  the  air  under  pressure  a  fairly  constant  supply 
of  air  can  be  relied  upon  for  daily  work.  This  system  for  transmitting  and  utilising  wind 
power  possesses  much  to  recommend  it  in  Egypt,  Westralia,  and  other  places  where  fuel 
and  water  are  scarce.  The  other  system  is  the  electric  transmission  system,  in  which  the 
wind  wheel  drives  a  dynamo-electric  generator,  from  which  wires  are  run  to  the  motor 
or  motors  where  the  power  is  required. 

Like  compressed  air,  it  requires  for  its  reliable  working  a  storage  reservoir,  in 
the  shape  of  an  electric  storage  battery.  And  as  the  speed  of  the  wheel  varies  with 
the  power  and  velocity  of  the  wind,  a  special  battery  must  be  used  capable  of  charging 
between  very  great  differences  of  electric  pressures,  so  as  to  make  use  of  all  winds 
blowing  between  10  and  30  miles  an  hour. 

The  problem  to  solve  in  the  storage  of  the  energy  of  the  wind  wheel  is  much  the 
same  for  compressed  air  and  electricity.  In  the  case  of  compressed  air  the  pump 
must  work  between  great  differences  of  speed  ;  and  as  the  torque  required  to  move 
its  pistons,  rods,  etc.  must  be  sufficient  to  work  it  at  a  lo-mile  breeze  speed,  it  is 
evident — this  torque  being  constant  at  all  speeds — the  speed  of  the  wheel  will  go  up 
nearly  as  the  square  of  the  wind  velocity,  and  the  increased  work  of  the  pump  will 
be  due  to  and  proportional  to  the  increased  speed  and  not  to  increased  torque  ;  the 
variation  in  speed  would  be  very  large.  A  variable  stroke  compression  pump  would 
greatly  reduce  this  large  variation,  but  that  is  a  difficulty  in  itself.  The  next  best 
solution  of  the  problem  is  to  use  a  compound  air  pump  with  three  or  four  cylinders 
and  pistons,  in  which  one,  two,  three,  or  four  pumps  may  be  worked  from  the  wind 
wheel, — one  on  the  lightest  breeze,  10  miles,  two  on  the  15-mile  speed,  three  on  the 
20-mile,  and  four  on  the  25-mile  speed, — each  pump  being  also  larger  in  capacity  than 
the  preceding  one.  By  this  means  the  speed  may  be  very  much  moderated,  for  the 
torque  required  increases  as  pumps  are  put  on,  so  that  the  work  done  is  proportional 
to  the  wind  pressure  or  torque. 

The  electrical  dynamo  generator  for  storing  electricity  into  the  battery  acts  to 
some  extent  (on  a  wind  wheel)  similarly  to  the  compound  pump.  If  the  speed  of 
the  dynamo  at  the  lowest  speed  of  the  wind  wheel  is  such  as  to  generate  an  electric 
pressure  slightly  greater  than  the  battery  pressure,  then  as  the  speed  increases  the 
torque  required  also  increases,  for  the  pressure  of  the  generator  and  the  current 
also  increases  into  the  battery.  Hence  the  speed  of  the  wind  wheel  is  opposed  by 


1 6  Modern  Engines 

this  increasing:  drag  put  on  by  the  generator,  and  the  variation  in  speed  much 
moderated.  For  the  purpose  the  dynamo  should  be  compound  wound  and  with 
field  magnets  far  below  saturation-point  at  the  small  load.  The  battery  must  be 
calculated  to  take  the  charging  current  at  the  maximum  speed  without  excessive 
heating. 

The  electrical  points  will  be  elucidated  under  their  own  headings. 
If  compressed  air  is  employed  for  transmitting  the  power,  then  some  further  con- 
siderations must  be  taken  into  account.  When  air  or  any  gas  is  compressed  by 
force,  sensible  heat  appears;  the  gas  is  raised  in  temperature  during  the  compression. 
The  question  as  to  whence  cometh  the  heat  is  an  important  one,  which  is  discussed 
under  the  science  of  heat.  In  the  meantime,  suffice  it  to  say  that  if  the  air  is  carried 
away  in  pipes  or  stored  in  a  reservoir  this  heat  is  dissipated  and  lost  by  conduction 
and  radiation,  and  the  condensed  gas  in  losing  the  heat  falls  in  pressure  to  some 
extent.  And  further,  we  shall  find  that  if  the  gas  is  afterwards  expanded  doing 
work  in  an  engine,  we  must  make  good  this  loss  of  heat  if  we  are  to  get  efficiency 
out  of  the  use  of  the  compressed  air ;  for  the  gas  on  expanding  must  get  back  the 
heat  produced  when  it  was  compressed,  and  if  this  amount  of  heat  is  not  supplied  to 
it  while  expanding  from  some  extraneous  source,  it  takes  the  heat  from  itself  and  the 
containing  pipes  and  cylinders  and  falls  in  temperature,  so  much  that  in  air  motors 

of  any  great  power  the  passages,  valves,  and  cylinders 
become  filled  with  ice  and  snow,  produced  from  the 
moisture  in  the  air  freezing  from  the  extraction  of  the 
heat  by  the  expanding  air. 

If  compressed  air  is  therefore  allowed  to  cool  down 
before  use  in  an  engine,  then  to  get  good  efficiency  we 
must  provide  some  source  of  heat  to  "reheat"  it  before 
it  enters  the  engine. 

In  fact,  this  absorption  of  heat  by  previously  com- 
pressed gas  which  has  been  cooled  under  compression  is 
IG'  7'~  the  fundamental  principle  upon  which  some  ice  making 

and  refrigeration  by  machinery  is  based.  Air  is  compressed  in  these  machines,  then  cooled 
as  much  as  possible,  then  expanded,  when  it  thereupon  falls  below  zero  temperature. 
This  freezing  air  is  then  led  through  vessels,  in  which  it  abstracts  the  heat  and  produces 
ice. 

In  the  air  transmission  of  power  not  only  is  the  ice  and  snow  a  nuisance  in  the 
engine,  but  it  reduces  the  efficiency,  for  the  mean  pressure  is  less  as  the  temperature 
falls.  Reheating  is  therefore  an  important  engineering  question  in  compressed  air 
power,  which  cannot  be  fully  gone  into  in  this  chapter,  but  we  may  refer  to  a  simple 
means  for  supplying  the  necessary  heat  suitable  for  simple  transmission  under  the 
considerations  of  wind  power. 

Into  the  supply  pipe  next  to  the  engine  a  steel  box  is  inserted  large  enough  to  hold 
an  oil  lamp  with  several  large  wicks.  The  box  has  a  movable  cover,  easily  secured, 
air  tight,  and  capable  of  withstanding  the  maximum  air  pressure  ;  under  these  conditions 
all  the  air  entering  the  engine  must  pass  over  the  lamp  wicks.  To  start  the  engine  the 
lamp  is  ignited,  the  cover  shut  down,  and  the  air  turned  on  ;  the  engine  starts,  and 
as  the  air  passes  over  the  lamp  it  maintains  the  combustion,  and  at  the  same  time 
heats  the  air  entering  the  engine.  This  is  an  example  of  an  internal  combustion 
heater  in  which  the  products  of  combustion  also  pass  into  the  engine.  There  is  no 
chimney  loss,  hence  it  is  very  efficient. 

The  efficiency  of  the  air  motor  is  much  improved,  and  no  troubles  from  ice  and  snow 
occur.  Diagram  Fig.  7  shows  the  apparatus. 

Wherever  wind  power  is  seriously  considered  it  is  worth  while  weighing  the  advan- 
tages of  the  two  systems  of  storage,  compressed  air  and  electric.  In  out  of  the  way 


Windmills 


places  compressed  air  seems  the  simpler  system  to  maintain,  as  it  is  wholly  mechanical 
in  operation  and  of  common  mechanism  in  construction  ;  while  the  electric  system  is 
the  more  flexible  in  application,  overhead  wires  on  poles  carrying  the  power  wherever 
required. 


CONSTRUCTION  OF  WIND  WHEELS 

The  old  wheels  had  only  four  or  six  sails  carried  on  poles  like  masts.  The 
sails  were  canvas  spread  on  a  brander  of  wood,  with  cords  and  pulleys  whereby 
the  sails  could  be  "reefed"  to  reduce  the  pressure  in  a  heavy  gale.  Wood  was 
the  material  used  throughout.  They  are  to  be  seen  yet  in  the  eastern  counties  of 
England,  and  several  good  examples  are  still  working  in  the  Orkney  Islands  grind- 
ing grain. 

The  modern  wheels  herein  illustrated  are  built  of  mild  steel,  strong,  compact,  and  of 
light  weight,  and  the  principles  of  design  are  the  same  as  those  of  a  water  turbine,  for 
they  are  fluid  pressure  turbines  of  a  simple  design. 

Properly  designed,  the  blades  of  the  wheel  should  be  made  of 
sheet  steel,  and  curved  so  as  to  gradually  change  the  direction  of 
the  air  stream  striking  them.  For  common  practical  work,  and 
owing  to  the  facility  with  which  they  can  be  feathered,  flat  blades 
are  used,  as  shown  in  Figs,  i  and  2.  Curved  blades  cannot  be 
turned  edge  on  to  the  wind,  so  that  in  a  heavy  gale  they  would 
be  damaged  ;  but  in  any  wind  wheel  of  importance  arrangements 
can  be  made  whereby  the  whole  wheel  can  be  turned  edge  on  to 
the  blast. 

The  blades  when  curved  should  be  shaped  like  the  blades  of 
a  parallel  flow  water  wheel,  as  shown  in  Fig.  5.  The  pump  to  be 
employed  for  compression  of  air  in  cases  where  that  system  of 
power  storage  is  adopted  must  be  simple  and  effective.  The  whole 
question  of  compressed  air  power  and  apparatus  will  be  fully 
treated  later  ;  meanwhile,  it  will  suffice  to  show  a  very  simple 
form  of  water  pump  suitable  for  the  windmill  (Fig.  8).  The  pump 
and  the  driving  shaft  are  fixed  conveniently  to  a  cast-iron  hollow 
column,  which  forms  a  receiver  of  small  capacity.  It  is  a  simple 
trunk  piston  pump  with  large  valves.  For  large  storage  of  air,  wrought-iron  drums 
are  of  greatest  capacity,  with  a  minimum  weight ;  those  should  be  made  of  a  size 
easily  transported,  and  a  number  connected  together  by  a  pipe  to  obtain  the  desired 
capacity. 

For  electric  storage  the  dynamo  chosen  should  be  a  series  wound  machine,  feeding 
into  a  battery  of  large  capacity,  and  the  terminal  electric  power  delivery  at  the  battery 
should  be  at  least  2  volts  less  than  the  dynamo  terminal  power  delivery  when  the  mill  is 
running  on  the  lowest  speed  it  may  be  designed  for,  and  an  automatic  cut-out  must  be  in 
circuit  in  order  to  open  the  circuit  the  moment  the  battery  and  dynamo  power  deliveries 
are  equal.  By  this  arrangement,  as  the  speed  increases  with  the  speed  of  the  wind, 
the  torque  will  increase  also. 

In  charging,  the  power  delivery  of  each  cell  may  be  2.5  volts,  and  may  be  2.7  volts  ; 
in  fact,  the  charging  volts  may  range  from  2.2  to  2.8  volts.  At  2.2  volts  the  current 
entering  the  cells  will  be  very  small,  while  at  2.8  volts  it  may  be  very  large,  the 
difference  of  0.6  volt  giving  a  large  current  through  the  cell's  very  small  resistance. 

The  cell  may  have  a  resistance  of  o.oi  ohm,  so  that  the  current  would   be    j^  =  6° 

amperes. 

Any  series  wound  dynamo  will  not  do  for  this  work.     Common  series  dynamos  are, 
VOL.  i. — 2 


FIG.  8.— Windmill 
Pump. 


1 8  Modern   Engines 


as  a  rule,  made  with  large  armatures  and  small  fields,  so  that  they  are  nearly  constant 
current  generators.  A  dynamo  for  a  windmill  must  have,  on  the  contrary,  a  large  field 
and  small  armature,  so  that  the  field  strength  goes  on  increasing  proportionally  with 
increased  speed.  Such  machines  are  not  to  be  found  in  stock,  but  must  be  specially 
designed  for  the  wind  wheel  to  be  used  with  it. 

Attempts  have  been  made  to  combine  two  machines  to  be  coupled  in  series  parallel 
for  different  speeds  on  a  windmill  to  be  carried  by  ships,  but  the  simple  series  dynamo 
specially  designed  is  much  better  and  far  simpler. 

The  electric  system  of  storage  is  the  best  for  wind  power,  and  is  well  worthy  of  the 
consideration  of  engineers  ;  while  the  compressed  air  system  offers  advantages  in  colonial 
and  outlying  work  where  the  electric  battery  and  motors  might  not  get  the  required 
skilled  attention. 

In  the  spring  of  this  year  the  Royal  Agricultural  Society  of  Great  Britain  took 
up  the  question  of  wind  engines.  The  following  particulars  and  illustrations  are  from 
their  report  thereon  : — 

Having  regard  to  the  increasing  demand  for  an  inexpensive  pumping  plant,  and 
the  very  material  alteration  in  the  design  of  the  modern  wind  engine,  the  society  decided 
to  institute  trials  of  wind  pumping  engines  in  competition  for  prizes,  so  that  trustworthy 
data  might  be  provided  for  the  guidance  of  intending  users.  No  independent  competitive 
trials  of  these  engines  have  previously  been  carried  out  in  this  country. 

As  the  use  to  which  these  engines  are  principally  applied  is  that  of  pumping,  and 
as  with  an  engine  running  for  several  hours  throughout  the  week  a  very  considerable 
amount  of  water  may  be  pumped  with  comparatively  small  power,  the  limit  of  4  horse- 
power was  decided  upon  as  a  maximum.  It  will  be  seen  from  the  results  of  the  trials 
that  this  was  a  very  ample  allowance,  as  none  of  the  competing  mills  attained  such 
power  under  the  stipulated  wind  velocity,  which  was  fixed  at  ten  miles  per  hour.  This 
velocity  is  considerably  in  excess  of  the  mean  velocity  at  inland  stations  throughout  the 
year  in  this  country.  On  the  other  hand,  there  are  periods  at  which  the  engines  should 
be  able  to  work  efficiently  at  very  much  higher  velocities.  It  was  obviously  undesirable 
to  fix  upon  a  high  wind  velocity,  as  it  is  all  important  that,  though  the  engine  should 
control  itself  and  work  efficiently  in  a  high  wind,  it  should  also  run  in  light  winds,  which 
are  generally  prevalent  during  the  driest  periods  of  the  year  when  there  is  the  greatest 
necessity  for  pumping. 

With  a  view  to  ensure  that  the  trials  should  be  held  under  the  most  variable 
conditions  as  to  wind  velocity,  they  were  fixed  to  take  place  during  March  and  April. 
The  records  of  the  wind  velocities  during  the  period  of  the  trials  proved  the  wisdom  of 
this  choice  of  season,  as  during  the  greater  part  of  the  time  there  was  plenty  of  wind, 
with  just  a  few  days  of  light  wind,  which  afforded  the  opportunity  that  was  desired  of 
comparison  between  the  several  engines  under  those  conditions. 

To  gauge  the  power  developed  by  each  engine,  it  was  stipulated  that  the  amount 
of  water  pumped  against  a  head  of  200  feet  should  be  measured,  and  that  such  should  be 
taken  as  the  standard  upon  which  to  compare  the  work  done  by  each. 

It  is  not  to  be  assumed  that  200  feet  head  is  in  any  way  the  average  head  at  which 
such  engines  would  ordinarily  work.  In  most  cases  they  would  raise  the  water  to  a  very 
much  smaller  height.  On  the  other  hand,  they  might  be  required  to  raise  water  to  a 
greater  height.  This  is  a  point  which  merely  affects  the  size  of  the  pump  ;  and  the 
particular  head  of  200  feet  was  adopted  in  order  to  keep  the  size  of  the  pump  and 
its  connections  within  moderate  dimensions ;  1 1  gallons  per  minute  representing  a 
horse-power. 

Twenty  -  two  competitors  entered,  and  the  tests  came  off  as  arranged  on  the 
society's  permanent  show  ground  at  Baling.  Sixteen  of  the  competitors  for  various 
reasons  dropped  out  of  the  contest  before  the  final,  and  six  entered  for  the  final  tests, 
with  the  result  shown  in  Table  III. 


Windmills 


TABLE   III.— PERFORMANCE   OF  WIND   ENGINES   IN   PUMPING   WATER. 


I. 

II. 

No.  3. 

No.  7. 

No.  8. 

No.  14. 

No.  16. 

No.  17. 

Goold, 

Shapley,  & 
Muir  Co. 

Messrs. 
Thomas 
&  Son. 

Mr.  John 
W.  Titt. 

Messrs. 
R.  Warner 
&  Co. 

Mr.  John 
W.  Titt. 

Messrs. 
Henry 
Sykes  Ltd. 

Price    .... 

£70 

£77 

£61,  75.  6d. 

^79 

<£/4,  i  os. 

^106 

Diameter  of  Wheel 

16  feet. 

1  6  feet. 

1  6  feet. 

1  6  feet. 

1  6  feet. 

1  6  feet. 

Wind 

1903. 

Velocity. 

Gallons. 

Gallons. 

Gallons. 

Gallons. 

Gallons. 

Gallons. 

March  4 

15 

3137 

3563 

5 

5 

1030 

343 

6 

10 

2752 

3950 

7 

12 

3019 

4207 

9 

12 

3151 

10 

8 

2214 

2045 

ii 

6 

1,428 

1181 

895 

12 

8 

2,545 

1913 

1733 

13 

9 

3,608 

2309 

2268 

14 

3 

15 

16 

15 

3772 

'7 

22 

3339 

18 

20 

2094 

3140 

4*35 

19 

20 

4746 

5653 

4203 

20 

18 

4520 

5250 

21 

18 

3912 

4874 

23 

22 

4525 

3640 

5244 

24 

12 

2781 

25 

15 

4210 

26 

25 

5445 

27 

8 

2,891 

1248 

28 

24 

10,047 

4447 

347° 

30 

22 

7»632 

4399 

31 

7 

3,160 

1850 

1373 

THE  PERFORMANCES  OF  THE  ENGINES 

In  accordance  with  the  regulations  the  following"  specific  points  were  taken  into 
account : — 

1.  The  design  and  stability  of  the  tower. 

2.  The  cost  of  the  foundations  and  the  price  of  the  engine  and  pump. 

3.  The  regulation  of  the  working  and  control  of  the  machinery. 

4.  The  automatic  governing  of  the  engine  in  varying  winds. 

5.  The  efficiency  as  represented  by  the  amount  of  water  delivered  under  the  specified 
conditions. 

6.  The  cost  of  maintenance  in  respect  of  repairs  incidental  to  ordinary  wear. 

7.  The  ease  of  erection. 

The  estimation  of  the  merits  of  the  several  engines  in  respect  of  these  seven  points 
depends  partly  upon  the  examination  of  the  designs  and  partly  upon  experience  of  the 
working  of  the  engines  during  the  trials. 

It  may  here  be  noted  that  the  performance  was  judged  upon  the  working  of  the 
engines  and  pumps  as  combined  machines.  The  selection  of  a  pump  inappropriate  for 


20 


Modern  Engines 


the  particular  engine  under  the  condition  of  the  trials  placed  the  competitor  in  a  most 
disadvantageous  position. 

Two  of  the  machines,  Nos.  14  and  17,  were  provided  with  arrangements  for 
adjusting  the  length  of  stroke  of  the  pump  while  running.  For  the  purposes  of  the 
competition  the  strokes  of  these  pumps  were  fixed,  at  the  outset,  at  the  length  estimated 
by  the  exhibitors  to  give  the  best  results  under  the  condition  of  the  trials,  and  were  not 


EXPLANATION. 

Number  of  revolutions  of  wheel. 
Number  of  strokes  of  pump. 
Quantity  of  water  in  galls. 
Slip. 


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PARTICULARS   OF   PUMPS. 

No.    3  =  4  inches  by  22  inches.  Double-acting. 

,,      7  =  4  „          8       ,,  Single-acting. 

>,      8  =  3i        „          64     „ 

„     14  =  3i         „          5       -.  Double-acting. 

,,     16  =  4-^         ,,  8       .,  Single-acting. 

,,    17  =  2^        ,,          8      ,,  Double-acting. 

NOTE. — Nos.  8  and  16  are  "  Bucket  and  Plunger  " 
Pumps. 


FULL   BORE   CAPACITY   PER  STROKE. 


No.    3 

7 


16 
17 


•  3636 

.183 

.348 

.4601 

.284 


gallons. 


RATIO   BETWEEN   WHEEL  AND   PUMP. 
No.    3         =         2^  to 


16 
17 


FIG.  9.— Diagram  Illustrating  the  Working  of  six  selected  Wind  Engines  during  Final 
Trials.     150  working  hours. 

subsequently  adjusted.     Credit  for  this  facility  of  adjustment  was  given  in  estimating  the 
design.     It  would  not  be  fully  represented  in  the  recorded  performance. 

Others  of  the  exhibits  had  arrangements  in  the  head  gear  for  adjusting  the  length 
of  stroke,  as  will  be  seen  from  the  descriptions  given  above. 


Tests  on  Windmills  2,1 

One  requirement  was  regarded  as  inexorable.  The  engine  and  pump  were 
expected  to  stand  the  strain  of  the  two  months'  run  with  only  such  attention  as  might 
be  supposed  to  be  available  on  the  spot  in  ordinary  conditions  of  working.  Any  break- 
down that  required  the  maker  to  be  called  in  to  get  the  machine  into  proper  working 
order  again  was  regarded  as  terminating  the  competition  so  far  as  that  machine  was 
concerned,  on  the  ground  of  inadequate  stability  and  durability. 

The  final  stage  of  the  competition  dealt  with  the  selection  of  two  mills  for  the 
First  and  Second  Prizes  respectively  from  among  the  selected  six.  The  diagram 
(Fig.  9)  represents  the  results  obtained  by  the  second  month's  run  of  the  six 
engines.  It  shows  the  number  of  revolutions  made  by  each  of  the  engines,  the 
number  of  strokes  of  the  pumps,  and  the  amount  of  water  pumped.  The  last  item  is 
indicated  in  the  diagram  by  the  length  of  the  full  black  column — the  third  column 
in  each  space.  Above  the  top  of  the  black  column  is  the  outline  of  an  addition  to 
its  height,  intended  to  show  the  loss  of  water  due  to  the  slip  or  defective  efficiency  of 
the  pump. 

In  order  to  give  further  indication  of  the  process  leading  up  to  the  decision,  it  is 
desirable  to  refer  to  the  several  points  to  which  specific  attention  was  paid,  and  with 
regard  to  these  to  record  the  following  notes : — 

i.  The  design  of  each  tower  was  examined.  Its  practical  stability  was  sub- 
jected to  severe  experimental  test  during  the  course  of  the  trials,  under  winds 
which  reached  45  miles  per  hour  in  one  instance, — a  very  high  velocity  for  an  inland 
exposure. 

Price  has  been  taken  into  account  in  relation  to  the  amount  of  water  which  can 
be  delivered  for  a  given  outlay.  The  price  is  to  a  considerable  extent  determined  by  the 
size  of  the  engine. 

In  the  efficiency  of  delivery  No.  3  stands  conspicuously  at  the  head  in  this  respect. 
No.  17  comes  next,  and  loses  not  a  little  by  the  inefficiency  of  the  pump  ;  then  follow 
No.  8,  No.  7,  No.  14,  and  No.  16,  in  the  order  named.  The  inefficiency  of  the  pump 
of  No.  14  placed  it  at  a  considerable  disadvantage  in  this  respect. 

With  regard  to  the  delivery  of  water,  it  should  be  remarked  that,  as  may  be 
inferred  from  its  design,  No.  3  delivers  water  equally  for  practically  every  part  of  the 
stroke.  There  is  hardly  any  idle  or  slack  time  in  the  revolution  of  the  wheel,  and 
consequently  the  engine  works  with  a  very  long  pump  stroke,  and  does  a  great  deal  of 
pumping  for  very  few  revolutions. 

The  pumps  of  the  six  engines  were  double  acting  pumps,  or  bucket  and  plunger 
pumps,  with  the  exception  of  that  belonging  to  No.  7,  which  was  single  acting. 
The  conditions  of  the  competition  were  favourable  for  the  use  of  double  acting 
pumps. 

In  forming  a  judgment  upon  the  cost  of  maintenance  in  respect  of  repairs,  regard 
has  been  had  not  only  to  the  excellence  of  design  and  workmanship,  but  to  the  probable 
wear  and  tear  under  what  may  be  called  "agricultural"  conditions.  In  this  respect  the 
number  of  revolutions  of  the  wheel  and  the  number  of  strokes  of  the  pump  for 
a  given  quantity  of  water  delivered  are  very  important  items,  as  in  ordinary  wear  it 
is  upon  these  two  that  the  life  of  the  engine  or  pump  depends.  In  both  these  par- 
ticulars No.  3  is  conspicuously  successful.  Then  follow  No.  16,  No.  7,  No.  14,  No. 
17,  and  No.  8.  No.  7  is  distinguished  by  the  uniform  thoroughness  of  execution  of  the 
design. 

The  ease  of  erection,  which  is  an  important  item  from  the  agricultural  point  of 
view,  as  it  involves  serious  considerations  of  expense,  has  been  estimated  partly  from  an 
inspection  of  the  designs  and  partly  from  experience  on  the  ground.  On  the  whole, 
No.  7  is  regarded  as  entitled  to  special  mention  in  this  respect,  and  No.  17  presented 
obvious  elements  of  disadvantage  from  this  point  of  view. 

Considering  Table  III.  and  Fig.  9,  we  get  the  performance  of  the  mills.     No.  3  is 


22 


Modern  Engines 


clearly  ahead  of  all  the  others  in  nearly  every  point,   and  easily  takes  the  first  prize. 
The  points  worthy  of  special  commendation  are — 

1.  Its  general  excellence  of  design,  especially  as  regards  the  engine  and  pump. 

2.  Its  efficiency  as  determined  by  the  amount  of  water  pumped. 

3.  Its  successful  governing. 

4.  The  arrangement  for  the  automatic  application  of  the  brake. 

5.  Its  economy  in  upkeep,  due   to   the  slow  motion  of  its  moving  parts,  and   its 
good  workmanship. 

6.  Its  reasonable  price. 

For  the  Second  Prize  a  similar  prominence  in  so  many  points  is  not  to  be  expected, 
but  when  the  qualifications  under  the   several   points   enumerated  are   all  taken  into 

account,  No.  7  stands  distinctly  ahead 
of  the  remaining  four.  The  points  for 
special  notice  with  regard  to  this  mill 
are — 

1.  The  generally  satisfactory  nature 
of  the  design  of  the  engine  and  of  the 
tower,  and  the  thoroughness  of  the  work- 
manship in  its  execution. 

2.  The  provision  of  an  efficient  brake. 

3.  The  comparative  economy  of  up- 
keep arising  from  the  soundness  of  the 
design,  and  the  comparatively  slow  motion 
of  the  pump. 

4.  The  ease  of  erection. 

5.  Its  reasonable  price. 

There  was  considerable  diversity  in 
the  details  of  the"  sails,  their  shape,  angles, 
and  areas,  and  the  trials  were  not  con- 
clusive as  to  the  best  form  ;  for  some  were 
evidently  good  mills,  but  handicapped 
by  the  conditions.  However,  the  form 
of  the  sails,  their  angles,  and  dimen- 
sions of  the  prize  winner  are  such  as  the 
experience  in  turbines  generally  would 
lead  one  to  adopt.  We  will  now  briefly 
describe  the  final  competitors,  beginning 
with 


FIG.  10. — No.  3  Windmill. 


No.  3. — Messrs.  Goold,  Shapley,  &*  Muir  Co.  Ltd.,  Brantford,  Ontario,  Canada. 

This  Canadian  engine,  illustrated  in  Figs.  10  to  12,  has  a  wheel  16  feet  in  diameter, 
with  18  blades  grouped  in  six  sections,  having  an  area  of  131.32  square  feet,  with  an 
available  clearance  area  of  67.93  square  feet  between  the  blades  and  30.88  square  feet 
at  centre  of  wheel. 

The  blades  are  fixed  after  the  American  fashion  of  threading  them  on  the  outer 
ring  and  fixing  them  thereto  by  means  of  a  stamped  steel  bracket  riveted  to  the  sail  and 
ring,  the  inner  end  of  the  blade  being  riveted  to  the  inner  ring.  This  method  probably 
gives  a  maximum  of  strength  for  a  minimum  of  weight,  but  it  is  open  to  the  objection 
that  should  the  middle  blade  of  any  one  section  of  the  wheel  fail,  in  order  to  dis- 
mantle and  replace  it  it  is  necessary  first  to  cut  off  the  adjoining  blade.  The 
wheel  is  mounted  on  a  horizontal  shaft  running  in  two  roller  bearings  of  6|  inches 
in  length.  The  boss  of  the  wheel  is  made  very  deep  in  order  to  allow  of  the  effectual 


Details  of  Windmills 


bracing-  of  the  arms,  but  in  order  to  avoid  consequent  increased  overhanging  the 
boss  is  recessed  at  the  back  and  the  roller  bearing  off  the  main  shaft  is  carried  well 
forward  into  it. 

The  gear  of  this  engine  differs  from  all  others.  The  object  to  be  attained  was  to 
get  as  long  a  stroke  of  pump  as  possible,  a  pinion  on  the  main  shaft  gears  into  a  mangle 
rack  of  such  a  length  as  to  give  one  stroke  of  the  pump  shaft  to  two  and  a  half  of  the 
wheel. 

This  g-ear  is  illustrated  in  Fig. 
n,  B,  C,  and  D.  It  will  be  seen  that 
there  are  two  vertical  parallel  racks, 
with  a  connecting-  semicircular  rack 
top  and  bottom,  in  which  the  pinion 
alternately  engages  ;  the  rack  is  alter- 
nately thrown  over  at  the  end  of  each 
stroke  by  means  of  cams,  thus  re- 
versing the  direction  of  the  travel  of 
the  pump  rod. 

The  rack  is  guided  between  four 
steel  rollers,  which  at  either  end  of 
the  stroke  engage  the  cams  ;  and  to 
ensure  the  even  working  of  the  pinion 
in  the  rack  a  steel  guide  plate  work- 
ing against  a  flanged  roller  is  pro- 
vided. 

The  swing  of  this  mangle  action 
is  only  if  inch,  consequently  there  is 
very  little  angular  motion  of  the  pump 
connecting  rod.  The  pump  rod,  which 
is  of  3  inches  square  white  maple,  is 
connected  to  the  rack  casting  by 
means  of  a  piece  of  if-inch  wrought- 
iron  pipe  guided  through  the  tower 
head. 

The  rpump  is  a  double  acting- 
syphon  pump,  4  inches  diameter  by 
22-inch  stroke,  the  working  barrel 
being  of  gun-metal  and  the  valves  of 
vulcanised  indiarubber. 

The  main  feature  of  this  engine 
is  the  method  adopted  of  governing, 
which  differs  entirely  from  that  of  any 
of  the  other  engines.  This  is  shown 
in  Fig.  n,  E.  On  the  frame  of  the 
wind  vane  a  lever  is  pivoted,  one  end 

being  controlled  by  a  spiral  spring  anchored  to  the  lower  frame  of  the  vane.  To 
the  other  end  of  the  lever  is  attached  a  chain  H,  connected  with  the  pull-in  wire, 
the  tightening  of  which  is  done  in  opposition  to  the  force  of  the  spring  and  pulls  the 
wheel  into  the  wind.  On  freeing  the  pull-in  wire,  or  in  the  event  of  the  breaking  of 
same,  the  spring  pulls  the  wheel  over  parallel  with  the  vane  ;  consequently  the  edge 
of  the  wheel  only  is  facing  the  wind  ;  at  the  same  time  the  brake  is  put  on  and  the 
mill  stops. 

The  tower  consists  of  four  angle  steel  posts,  with  five  intermediate  angle  iron  frames 
and  diagonal  tie  rods.  At  the  bottom  of  each  post  are  anchor  plates,  which  are 


FlG.  ii. — Details  of  No.  3.     The  Prize  Winner. 


Modern  Engines 


bolted  to  the  timbers  let  into  the  ground  about  5  feet  deep.     The  general  design  and 
workmanship  of  this  engine  leaves  little  to  be  desired. 

This  engine  was  started  on  Monday,  March  2,  and  ran  most  satisfactorily  all 
through  the  trials.  At  the  end  of  the  first  month  it  was  one  of  the  selected  six,  and 
ultimately  gained  the  First  Prize. 

No.  7. — Messrs.  Thomas  &  Son,  64  Broad  Street,  Worcester. 

This  engine  is  illustrated  in  Fig.  14.  The  wheel  is  16  feet  in  diameter  with 
24  blades,  having  141.55  square  feet  area,  with  an  available  clearance  space  be- 
tween same  of  55.5  square  feet,  and  23.04  square  feet  area  at  centre  of  wheel.  The 
blades  in  this  wheel  are  separately  riveted  to  brackets  fastened  to  the  rings  of  the 


t<- 91-10" *4 


Utfj 

_:^>j_  _L  _^i  _'  _"^s4_  "J.  _^^v     JL    SA1* 

i     /  *     r         '«  ' 

j- 7-/3fe JT  -  -  -/-/.% -j 7-7** 1 

FIG.  12. — No   3.     Details  of  Sails. 

wheel,  so  that  any  one  blade  may  be  easily  removed  and  another  fixed  in  its  place.  The 
outer  end  of  the  blades  are  very  materially  strengthened  by  having  two  corrugations, 
which  are  seen  in  the  illustration.  The  wheel  is  further  stiffened  by  six  stay  rods  from 
the  outer  ring  of  the  wheel  to  a  casting  on  the  projection  of  the  wheel  spindle. 

Immediately  behind  the  wheel  is  an  automatic  band  brake,  which  is  actuated  by  a 
projection  on  the  tail  vane  when  it  is  blown  over  by  a  gust  of  wind,  or  when  the  wheel 
is  pulled  out  of  the  wind  by  the  windlass. 

The  wheel  spindle  is  carried  in  two  horizontal  roller  bearings  of  ample  propor- 
tions, and  the  thrust  of  the  wheel  is  taken  by  ball  bearings  at  the  end  of  the  spindle. 
The  tail  vane  itself  is  mounted  on  ball  bearings.  On  the  wheel  spindle  a  pinion  is 
keyed,  which  gears  into  a  wheel  on  the  pump  crankshaft,  speeded  so  as  to  give  one 


Details  of  Windmills 


stroke  of  the  pump  for  two  and  a  half  revolutions  of  the  wheel.  The  teeth  of  these 
wheels  are  all  tooled,  being  cut  out  of  the  solid.  The  cast-iron  revolving  head  is 
carried  on  ball  bearings  at  the  cap  of  the  tower,  and  a  cylindrical  sleeve  descends 
through  the  tower  head  and  is  guided  by  four  rollers.  This  gives  a  very  efficient  support 
to  the  head.  The  pump  rod  is  of  i-inch  wrought-iron  tube,  the  weight  of  which  is 
counterbalanced  by  a  vibrating  lever  and  weight. 

The  tower  consists  of  four  angle  posts  inclined  approximately  i  to  5,  with  angle  iron 
stiffening  frames  every  5  feet,  and  f  inch  diagonal  bracing  rods.  Placing  the  stiffening 
frames  at  the  intervals  named  materially  facilitates  the  work  of  erection,  as  the  tower 
forms  its  own  scaffold  as  the  work  proceeds. 

The  pump  is  of  the  single  acting  type,  fitted  with  gun-metal  bucket  and  suction 
valves. 

The  design  and  workmanship  both  in  the  engine  and  tower  were  most  carefully 
thought    out    and    executed,    and    throughout    the 
trial  the  engine  worked  very  satisfactorily,  and  was 
ultimately  awarded  the  Second  Prize. 

No.  8.—  Mr.  John  Wallis  Titt,  Warminster. 

The  wheel  of  this  engine  is  16  feet  in  diameter, 
sail  area  113.89  square  feet,  clearance  area  between 
blades  74.59  square  feet,  and  38  square  feet  area  at 
the  centre  of  the  wheel. 

The  stroke  of  the  pump  can  be  varied.  The 
wheel  is  mounted  on  a  crankshaft  with  roller 
bearings.  The  head  is  built  of  steel  angles  and 
plates,  and  revolves  on  roller  bearings. 

Another  point  in  this  mill  is  the  provision  of 
a  ladder  revolving  with  the  head  gear,  so  that  a 
man  can  without  danger  lubricate  or  attend  to  other 
small  matters  in  connection  with  the  gear  while  the 
engine  is  running. 

The  wheel  is  controlled  by  a  tail  vane  and 
weighted  lever.  This  lever  is  raised  by  the  starting 
wire,  which  passes  up  through  the  centre  of  the  mill 
and  over  two  small  guide  pulleys.  During  the  trial 
the  wire  failed,  and  the  absence  of  any  brake  on 
this  gear  was  very  apparent.  The  general  arrange- 
ment of  the  head  is  shown  in  Fig.  13. 

The  pump  is  of  the  bucket  and  plunger  type,  3^  inches  diameter  and  6^  inches 
stroke,  and  there  being  no  intermediate  gear  the  efficiency  of  the  pump  was  good. 
At  times,  however,  the  speed  of  the  pump  is  high,  and  unless  the  plunger  is  properly 
lubricated  it  would  tend  to  wear  more  than  a  slower  running  pump. 


FIG.  13.— No.  8.    Mr.  John  W.  Titt's  Mill. 


No.  17. — Messrs.  Henry  Sykes  Ltd. ,  66  Bankside,  London,  S.E. 

This  engine  presents  several  novel  features  which  had  evidently  been  carefully 
thought  out. 

Unlike  other  engines  having  fixed  blades  in  their  wheels,  in  which  the  tendency  is 
rather  to  increase  the  size  of  the  blades  and  to  diminish  their  number,  the  opposite 
course  is  adopted  of  diminishing  the  width  and  increasing  the  number  of  the  sails,  on  the 
ground  that  most  work  is  done  by  the  wind  on  the  leading  edge  of  the  blade  ;  and 
consequently  it  is  well  to  have  as  many  leading  edges  as  practicable.  The  periphery  of 


26 


Modern  Engines 


the  wheel  has  a  hoop  round  it,  to  which  the  end  of  the  blades  is  fixed,  which  gives  it  a 
very  strong-  and,  at  the  same  time,  neat  appearance.  Another  novel  feature  of  the 
engine  is  the  jointed  tail  vane,  described  later. 

The  wheel   is   16   feet   diameter,   with   42   blades  4  feet  6  inches   long,  9   inches 


FIG.  14. — No.  7.     Messrs.  Thomas  &  Son's  Mill.     Second  Prize. 

wide  at  the  periphery,  and  6  inches  at  the  inner  end.  The  sail  area  is  142.82  square 
feet,  with  54  square  feet  available  clearance  between  them,  and  38.48  square  feet 
at  the  centre.  The  curvature  of  these  blades  is  shown  in  Fig.  16.  The  wheel  is 
mounted  on  a  plain  single-throw  crankshaft,  carried  in  an  inclined  position  in  two 
gun-metal  bearings  in  the  revolving  head,  the  thrust  of  the  wheel  being  taken  by  a 


Details  of  Windmills 


2.7 


collar  on  the  shaft,  bearing  against  the  side  of  the  main  gun-metal  bearing.     The  head 
revolves  on  roller  bearings. 

The  tail  vane  is  mounted  on  two  rods  attached  to  the  revolving  head,  which  always 
tends  to  make  the  wheel  face  the  wind,  the 
inclined  hinged  axis  of  vane,  a  fixed  portion 
of  tail  vane,  and  a  side  vane,  which  tends 
to  make  the  wheel  face  away  from  the  wind 
and  only  present  its  edge  to  it. 

Diagram  Fig.  15  shows  the  position 
of  the  wheel  and  vanes  when  the  engine 
is  running  in  a  moderately  light  wind,  the 
wheel  facing  the  wind. 

We  need  not  describe  more  of  them 
from  the  report,  but  may  notice  the  head 
gearing  of  the  "Samson"  Mill  by  Messrs. 
J.  S.  Millar  &  Sons,  Annan. 

This  "Samson"  mill  is  very  similar  to 
the  "  Ideal"  mill ;  the  wheels  are  the  same, 
but  the  gearing  is  somewhat  different,  in  that 
two  small  pinions  on  the  wheel  shaft  gear 
into  two  wheels  with  a  pin  between,  forming 
the  crank  for  the  pump  rod,  taking  the  place 
of  the  annular  gear  in  the  "  Ideal  "  mill.  The 
governing  arrangements  are  the  same  in 
each.  The  "  Samson  "  tower  is  of  the  same 

design,    but   is   a  4-post   tower   instead   of  FlG>  I5._Details  of  No.  17. 

tripod.     The  gearing  is  illustrated  in  Fig.  17.  Henry  Sykes'  Mill. 


i 

FIG.  16. — No.  17.     Henry  Sykes'  Mill.     Details  of  Sail. 


Modern  Engines 


An  exceedingly  simple  little  windmill 
(Fig.  18)  may  be  constructed  of  two  half 
discs  of  sheet  metal,  zinc  for  preference, 
or  aluminium.  The  sails  are  at  right 
angles  to  each  other,  and  the  shaft 
passes  between  at  an  equal  angle  to 


FIG.  17. — Windmill  Head  Gear. 


FIG.  18.— Simple  Windmill. 

each  sail.  It  works  best  with  the  shaft 
parallel  with  the  wind.  The  half  discs 
are  tied  to  the  shaft  and  to  each 
other  by  steel  wires,  as  shown.  It 
has  been  called  by  a  fanciful  name,  the 
Pantanemone. 


HYDRAULIC   MACHINES 

The  turbine  wheel  has  completely  superseded  the  water  wheel.  For  all  falls  of  water 
the  turbine  can  be  designed  to  give  better  results. 

In  Switzerland  and  in  the  United  States  of  America  water  powers  to  great  extent 
are  used.  In  1880  there  were  55,000  water  wheels  working  in  North  America,  with 
a  total  aggregate  power  of  2,000,000  horse-power.  Since  then  this  has  been  largely 
increased  by  the  introduction  of  electrical  transmission,  so  that  the  horse-power  is  now 
considerably  over  2,000,000. 

At  Geneva  water  power  to  the  extent  of  over  7000  horse-power  is  derived  from  the 
Rhone,  and  12,000  horse-power  more  from  the  same  river  about  5  miles  farther  down 
the  stream. 

In  the  British  Isles  there  are  no  great  falls  of  water,  but  in  the  more  hilly  and 
mountainous  districts  water  powers  could  be  developed  of  quite  considerable  amounts 
in  Wales,  Ireland,  and  North  Scotland.  Coal,  however,  is  cheap  and  plentiful,  so  that 
the  available  water  powers  are  neglected. 

Water  power  has  been  estimated  to  cost  in  America  about  ^4,  los.  per  horse-power 
per  annum,  and  steam  power  from  coal  at  8s.  a  ton  costs  about  the  same.  This,  however, 
is  for  low  falls  ;  for  high  falls  the  cost  is  much  less,  and  in  some  falls  over  100  feet  it  has 
been  as  low  as  £2  per  horse-power  per  annum. 

The  first  cost  of  water  power  varies  very  much  with  the  district  and  conditions,  and 
cannot  be  laid  down  on  any  fixed  basis.  The  large  works  at  Geneva  cost  ^30  per 
horse-power,  the  smaller  works  £60  per  horse-power. 

With  water  power  the  bulk  of  the  cost  is  due  to  rental  of  land  and  water  rights, 


Hydraulic  Machinery 


interest  on  capital  and  depreciation  of  plant,  only  a  small  fraction  for  working"  expenses  ; 
with  steam  power  about  half  the  cost  is  due  to  wages  and  fuel,  and  the  other  half  to 
permanent  charges. 

A  steam  plant  therefore  costs  less  when  idle,  whereas  in  a  water  power  plant  costs 
go  on  all  the  time  full.  If  the  water  cannot  be  used  night  and  day  the  whole  cost  falls 
upon  the  hours  during  which  it  is  used. 

Storage  of  water  is  of  great  importance  in  all  water  powers,  and  in  some  cases  it  is 
the  simplest  and  best  means  for  storing  power  to  pump  water  up  to  a  high  reservoir  ; 
and  in  some  cases  hydraulic  accumulator  storage  can  be  utilised  where  a  high  level 
reservoir  is  not  available.  Lord  Armstrong's  high  pressure  hydraulic  distribution  of 
power  system  is  a  good  example  of  this  method. 

The  hydraulic  accumulator  is  simply  a  tall  cylinder  with  a  heavily  loaded  ram, 
as  shown  in  Fig.  19.  The  water  is  pumped  in  continuously  in  small  quantity,  and 
maintained  under  the  pressure  of  the  load  on  the  ram,  the  ram  rising  and  falling  as 


FIG.  19. — Hydraulic 
Accumulator. 


FIG.  20. — Hydraulic  Crane. 


FlG.  21. — Hy- 
draulic Tele- 
scopic Lift. 


the  pressure  water  is  used  up  or  stopped.     If  a  is  the  area  of  the  plunger  or  ram,  and 

P 
P  the  load  upon  it,  then  -  =p,  the  pressure  per  square  inch  on  the  water  delivered  in 

Ibs.  If  L  is  the  length  of  the  cylinder  full  of  water,  then  aL  is  the  maximum  storage, 
and  the  energy  stored  in  foot-lbs.  is  equal  to  the  quantity  of  water  stored  multiplied 
by  the  pressure  per  square  foot. 

Thus  one  of  the  accumulators  in  the  London  Hydraulic  Power  Company's  station, 
working  at  a  pressure  of  100,000  Ibs.  per  square  foot  with  a  2O-inch  ram,  a  =  2.  2  feet, 


and  a  stroke  of  23  feet,  the  energy  stored  is  only 


2    2  X   TOO  OOO  X 


r 

=  2.5  horse-power  for 


-^ 
33,000  x  60 

an  hour. 

But  it  could  deliver  this  energy  very  quickly.  In  one  minute  it  would  work  at  the 
rate  of  150  horse-  power. 

It  is  a  costly  storage  apparatus,  but  for  the  purposes  to  which  it  is  applied  its  great 
rate  of  discharge  for  a  short  period  makes  it  worth  the  money.  This  form  of  hydraulic 
storage  is  used  largely  for  lifts  and  cranes,  and  an  excellent  but  small  system  exists  in 


30  Modern  Engines 

Glasgow  and  London  very  successfully.  At  Birkenhead  Docks  and  Woolwich  Arsenal 
hydraulic  cranes  are  so  worked.  A  simple  hydraulic  accumulator  will  work  a  number 
of  cranes  and  hoists. 

In  hydraulic  cranes  the  ram  carries  a  sheave  of  pulleys  with  chains  for  multiplying1 
the  motion,  as  shown  in  Fig.  20.  The  chain  is  fixed  at  F,  passes  over  one  pulley  at  D 
on  the  ram,  then  round  fixed  pulley  M,  and  again  over  D,  and  from  thence  over  guide 
pulleys  C,  A,  B  to  weight  W.  A  chain  H  driven  by  a  separate  ram  is  used  for  slewing 
the  jib. 

The  hydraulic  lift  as  now  most  commonly  made  has  a  telescopic  ram,  one  being 
fitted  inside  of  the  other  as  shown  in  Fig.  21,  so  that  when  closed  down  only  a  shallow 
well  beneath  is  necessary  to  accommodate  a  high  lift.  Thus  with  one  cylinder  and 
three  concentric  rams,  each  lifting  10  feet,  a  height  of  40  feet  may  be  obtained.  In 
Richmond's  patent  differential  telescopic  high  lift  hydraulic  lift  the  water  under  each 
piston  is  forced  into  the  next  cylinder  above,  so  that  the  rams  all  travel  up  simultaneously 
at  same  speed,  all  reaching  the  top  at  same  time.  This  is  by  far  the  best  and  safest  lift, 
and  is  the  only  one  to  be  recommended  for  heavy  passenger  work. 

WATER  PRESSURE  ENGINES 

These  are  of  two  classes,  reciprocating  pumping  and  blowing  engines  and  engines 
with  rotatory  shafts  and  cranks.  In  the  design  of  these  engines  it  must  be  borne  in 
mind  that  water  is  a  heavy  inexpansible  fluid,  which  has  considerable  inertia,  reacting 
on  anything  which  it  meets  to  divert  its  course  of  motion.  Many  water  pressure  engines 
have  been  designed  without  regard  to  this  elementary  fact,  and  with  certainty  of  failure. 

The  simplest  form  is  that  designed  to  work  a  bellows  or  pump  by  a  to-and-fro 
movement  only.  The  more  complex  forms  are  those  producing  rotary  motion.  A 
moving  column  of  water  has  velocity  and  pressure,  and  head  or  elevation,  i.e.  the  differ- 
ence in  level  between  the  place  where  it  starts  from  to  the  place  it  falls  to. 

The  total  energy  is  the  sum  of  its  momentum,  its  pressure  head,  and  elevation  head. 
If  V  is  the  velocity  in  feet  per  second,  p  =  pressure  in  Ibs.  per  square  foot,  A  =  the 
elevation,  and  g=  the  weight  per  cubic  foot,  the  total  energy  per  Ib.  of  water  is  equal  to 

\7-2  j. 

L^+P-  +  h  in  feet. 
2£-     g 

All  hydraulic  engines  are  arranged  to  work  with  one  or  other  of  these  quantities.  For 
example,  in  an  old  overshot  or  breast  wheel  the  water  drops  into  the  buckets  at  the  high 
level  with  as  little  force  as  possible,  only  falling  a  few  inches  into  the  buckets  ;  it  then 
merely  acts  by  its  dead  weight  on  the  loaded  side  of  the  wheel  ;  the  energy  is  simply 
proportional  to  h  x  w,  that  is,  height  of  fall  multiplied  by  the  weight  falling.  A  cubic 
foot  weighs  62.5  Ibs.  roughly,  and,  falling  in  a  bucket  a  height  of  10  feet,  would  give 
62.5  x  10  =  625  foot-lbs. 

The  pressure  head  is  used  in  all  piston  engines.  Here  the  water  flows  from  the  high 
level  at  a  slow  speed  through  a  pipe,  the  pressure  on  the  piston  is  that  due  to  the  height 
of  the  column  of  water  ;  thus  a  lo-foot  head  would  give  a  pressure  of  625  Ibs.  per 
square  foot  on  a  piston  at  the  bottom  ;  thus  we  can  utilise  /»,  the  pressure. 

In  the  third  method  we  utilise  V,  the  velocity.  In  this  case  the  water  is  allowed  to 
flow  with  the  full  velocity  due  to  the  pressure,  and  to  strike  against  a  free  moving  blade 
or  vane,  which  arrests  its  motion  and  turns  the  jet  aside.  The  energy  at  any  velocity  V 

.    mV2  — 

is    -_  —  .     If  we  take  a  lo-foot  fall,  again,  we  find  the  V  for  this  fall  to  be  equal  to  8  ^h 


_ 


_  V2  2v22 

^8  ^10  =  25.  2  =  velocity,    and    —  =  energy  per  Ib.     Hence  -^-  -=  10  approximately,  the 

energy  per  Ib.  of  water,  so  that  the  cubic  foot  would  have   10x62.5  =  625  foot-lbs.  of 
energy.     It  will  be  seen,  then,  that  we  get  the  same  amount  of  energy  out  of  every  cubic 


Hydraulic   Engines 


foot  of  water  at  the  same  fall  whether  it  acts  by  A,  its  dead  weight  on  a  wheel,  or  by 
pressure  p  on  a  piston,  or  by  velocity  V  on  a  vane  or  movable  blade. 

In  some  water  power  engines  we  have  p  and  V  acting  together,  as  in  Professor 
James  Thomson's  vortex  turbine. 

In  the  water  pressure  engines  now  under  consideration  p  is  the  acting  force,  V  being 
kept  below  2  or  3  feet  per  second  by  using  large  supply  pipes  and  ports. 

Hydraulic  pressure  engines  are  only  to  be  used  for  very  high  pressures  and  for  slow, 


FIG.  22. — Hydraulic  Engine. 

steady  motion.  The  volume  of  water  used  per  stroke  by  pressure  engines  is  constant, 
however  much  energy  is  exerted.  Water  can  be  saved  only  by  reducing  the  number  or 
length  of  strokes  on  small  load.  The  efficiency  at  full  load  is  about  80  per  cent.,  at 
half-load  under  35  per  cent.  To  get  over  this  difficulty  many  devices  have  been  proposed, 
such  as  the  use  of  two  or  more  cylinders  in  cranes  or  lifts,  so  that  for  light  loads  one 
cylinder  is  used,  and  for  full  load  all  the  cylinders  are  used. 

For  pumping  water  the  load  is  constant,  hence  a  simple  single  cylinder  is  used,  and 
also  for  bellows  blowing,  such  as  shown  in  Fig.  22. 


FIG.  23. — Hydraulic  Engine. 


FIG.  24. — Hydraulic  Engine. 


The  first  successful  engine  of  this  type  was  probably  that  of  the  design  by  Mr.  Joy, 
who  applied  the  auxiliary  valve.  There  being  no  rotary  motion,  the  valves  must  be 
operated  in  the  first  instance  by  some  tappet  motion,  like  that  shown  in  Fig.  23,  in 
which  the  piston  B  makes  the  little  valve  rods  projecting  through  the  cylinder  cover 
move  when  it  comes  to  either  end  of  its  stroke.  Now,  if  these  rods  are  made  to  actuate 
a  slide  valve  like  D  direct,  there  being  no  momentum  and  no  expansion,  as  soon  as  the 
valve  opens  very  slightly  the  piston  stops  and  the  valve  ceases  to  open  ;  hence  only  a 
small  amount  of  water  flows  and  the  speed  is  restricted. 


Modern  Engines 


The  idea  of  the  auxiliary  valve  is  to  provide  a  small  easily  worked  piston  to  which 
the  tappets  admit  water  under  pressure.  This  auxiliary  piston,  having  only  to  move  the 
D  valve,  moves  easily  and  quickly,  and  being1  balanced  by  a  piston  or  other  means  moves 
with  little  friction,  and  opens  the  ports  full. 

Another  form  with  a  rotary  auxiliary  valve  is  shown  in  Fig.  24,  the  valve  being 
operated  by  a  tumbler  motion  which  falls  over  and  opens  the  valve  wide. 

In  organ  blowing  engines  the  auxiliary  valve  may  with  advantage  be  operated  by 
air  pressure  from  the  bellows  and  started  by  a  hand  valve. 

The  rotary  shaft  engines  are  usually  oscillatory,  thus  obtaining  a  very  simple  valve 
mechanism.  One  which  has  been  much  used  is  that  shown  in  Fig.  25,  the  Schmidt 
engine.  The  oscillation  of  the  cylinder  opens  and  shuts  the  ports  ;  the  cylinder  is  carried 

on  trunions  E,  concentric  with  the 
curved  faces  of  the  valves.  These 
trunions  are  carried  on  stiff  levers 
pivoted  to  the  bed,  and  by  means  of 
screws  can  be  depressed  so  as  to 
keep  the  valve  faces  close  up  as  they 
wear  away.  An  air  vessel  is  also 
provided  on  the  supply  to  give  some 
elasticity  and  prevent  shocks. 

In  Hastie's  engine  we  have  an 
example  of  an  effort  to  construct  a 
3  -  cylinder    engine    with    a   variable 
piston  stroke,  so  that  the  water  used 
will   be   more   in   proportion  to  the 
work  done,  and  it  met  with 
.some  degree  of  success.     The 
crank    pin    is    moved    on    a 
slide  against  the  tension  of 
springs,  so  that  the  greater 
the  resistance  offered  by  the 
load     the     longer     becomes 
the   centre   of  the  pin  from 
the  crank  shaft  centre,  and 
hence  the  greater  the  lever- 
age  of  the   piston   and   the 
longer  the  stroke. 

In  the  same  direction  of 
improvement  a  later  type  of 
engine  has  been  developed 
by  Mr.  Arthur  Rigg  with 
four  cylinders.  In  Hastie's 
engine  the  cylinders  were 

oscillatory,  but  otherwise  stationary  while  the  crank  revolved.  In  Rigg's  engine  the 
crank  pin  does  not  revolve,  but  is  capable  of  a  lateral  movement  horizontally,  while 
the  cylinders  revolve  round  the  pin  and  also  oscillate.  The  plungers  are  pivoted  to 
a  revolving  crank  disc,  as  shown  in  Fig.  26.  If  the  central  hollow  pin,  which 
also  acts  as  valve,  is  central,  then  the  engine  stands  still,  and  if  moved  to  one  side 
excentric  ;  the  length  of  the  stroke  is  twice  the  eccentricity.  The  central  pin  is  carried 
on  differential  hydraulic  plungers,  by  means  of  which  it  can  be  moved  horizontally  to 
right  or  left.  There  are  two  ports,  an  exhaust  and  pressure  port,  on  the  central  boss, 
which  is  faced  to  press  against  the  fixed  ports,  and  each  cylinder  receives  water  during 
one-half  of  a  revolution  and  exhausts  during  the  other  half. 


FIG.  25. — Schmidt's  Hydraulic  Oscillating  Engine. 


o 


Water  Turbines 


33 


If  the  pin  is  moved  to  one  side  the  disc  revolves  in  one  direction,  and  if  moved  to 
the  other  side  it  revolves  in  the  opposite  direction,  and  the  stroke  and  consumption  of 
water  is  adjusted  to  the  work  to  be  done. 

In  Hastie's  engine  the  adjustment  of  stroke  is  automatically  proportionate  to  the 
load  ;  the  Rigg  engine  requires  to  be  adjusted  by  hand  by  valves  to  the  load. 

The  water  enters  by  pipe  on  the  left  hand,  and  by  the  hollow  plunger  reaches  the 
plung-er  ports.  The  water  pressure  in  the  open-ended  hollow  ram  tends  to  move  the  ram 
to  the  right,  while  the  right-hand  larger  plunger  can  be  moved  to  the  left  by  admitting 
water  pressure  ;  the  water  is  admitted  to  or  released  from  the  larger  plunger  by  two 
valves,  so  that  it  can  be  adjusted  at  any  point,  and  by  shutting  both  valves  the  plunger 
is  locked  in  position. 

A  small  engine  with  2|-inch  rams  working  at  700  revolutions  per  minute  at  500  Ibs. 
pressure  runs  well,  and  has  power  enough  to  work  a  heavy  crane. 

These  and  other  hydraulic  pressure  engines  have  a  very  limited  sphere  of  useful- 
ness, although  of  much  importance  wherever  they  can  be  used,  such  as  for  intermittent 
work.  The  high  pressure  of  accumulators  is  required  to  give  them  power,  and  the 
internal  strains  are  very  great,  so  that  they  are  heavy  machines  and  somewhat  costly. 


FIG.  26. — RiggT  s  Engine. 

An  hydraulic  system  for  working  hydraulic  cargo  lifts  and  cranes  is  exceedingly 
useful  on  steamships,  as  they  work  silently,  efficiently,  and  with  a  maximum  of  safety, 
and  do  not  create  the  intolerable  clatter  and  noise  raised  by  the  steam  winch. 


WATER  TURBINES 

This  class  of  hydraulic  machinery  is  the  important  one.  They  have  been  roughly 
sorted  into  classes  according  to  the  direction  of  the  water  flow  in  relation  to  the  turbine 
wheel.  As  a  matter  of  fact,  it  makes  little  difference  whether  the  flow  is  in  one  direction 
or  another ;  but  the  classification  serves  as  a  brief  description  of  the  general  arrange- 
ment of  the  machine. 

We  have,  ist,  axial  flow  turbines,  in  which  the  water  flows  parallel  to  the  axis  of 
the  wheel. 

2nd.  Inward  radial  flow  turbines,  in  which  the  water  flows  in  radially  from  the  outer 
to  the  inner  periphery. 

3rd.  Outward  radial  flow  turbines,  in  which  the  water  flows  from  the  inner  to  the 
outer  periphery. 

4th.   Mixed  flow  turbines,  in  which  the  water  flows  radially  and  axially. 

5th.   Free  jet  turbines  or  tangential  flow  turbines,  in  which  a  jet  or  jets  of  water 
strike  the  buckets  or  vanes  tangentially. 
VOL.  i. — 3 


34 


Modern  Engines 


GUIDE  BLADE 


energy    m 


FIG.  27. — Diagram  of  Pressure  Turbine. 


But  the  real  fundamental  classification  of  turbines  divides  them  into  two  classes 

only — 

ist.   Pressure  turbines. 
2nd.  Impulse  turbines. 
The  first  act  partly  by  the  pressure  of  the  water  and  partly  by  its  momentum,  that 

is,  by  V  and  p.     When  the  water  enters  the  turbine  it  has  pressure,  as  all  the  energy  of 

the  fall  has  not  been  developed  into  velocity.     It  has  velocity  also,  which  it  loses  in 

passing-  through  the  turbine,  giving 
up    the    corresponding- 
doing  so. 

As  there  is  pressure  on  the  water 
as  it  enters  it  must  fill  the  whole 
turbine  case,  which  must  be  water- 
tight except  at  the  outflow ;  the 
water  must  act  on  the  whole  wheel. 
In  the  second  class  the  whole 
head  of  water  is  developed  into  a  jet 
or  jets  of  great  velocity,  due  to  the 
fall ;  such  jets  have  no  side  pressure. 
This  may  be  seen  by  simple  inspec- 
tion, for  a  free  jet  moves  for  a  dis- 
tance from  the  orifice  as  a  straight 
rod  of  water,  not  expanding  side- 
ways as  it  would  do  under  pressure. 
Water  under  pressure  transmits  that  pressure  sideways,  forward,  and  in  every 

direction  ;  but  in  a  column  of  water  moving  at  the  full  velocity  due  to  the  head  there  is 

no  side  pressure,  the  whole  energy  is  in  the  forward  movement. 

Pressure  turbines  work  best  when  drowned,  so  that  no  part  of  the  fall  is  lost.     But 

they  will  work  equally  well  up  to  25  feet  above  the  tail  race  if  the  outflow  pipe  mouth  is 

carried  down  below  the  tail  water  surface,  this  part  of  the  fall  being  utilised  by  the 

suction  of  the  water  falling  down  the  pipe.     Acting  like  a  syphon,  this  outflow  tube  is 

called  a  draught  tube.     This  facility  is  of  value  in  many  cases,   for  it  is  not  always 

advisable  nor  possible  to  have  the  turbine 

at  the  tail  water  level.     And  when  the 

tail  water  level  is  variable  in  height  this 

draught  tube  allows  of  the  rise  and  fall 

of  the  level  without  affecting  the  turbine, 

except  to  reduce  the  suction  when  the  tail 

water  level  rises.     Whereas  the  impulse 

turbine  must  be  placed  above  the  highest 

level  of  the  tail  water,  it  will   not  work 

drowned  ;  hence  the  whole  fall  cannot  be 

utilised  at  low  water  level  in  the  tail  race. 
Some  turbines  have  been  designed  to 

work  as  impulse  and  pressure  turbines,  so 

that  when  the  tail  water  is  low  they  work  by  impulse,  but  when  high  and  the  wheel 

drowned,  work  as  pressure  turbines.     Such  turbines  are  called  "limit  turbines."     They 

are  not  successful ;  it  is  by  far  better  to  use  a  pressure  turbine  with  a  draught  tube  long 

enough  to  keep  the  wheel  above  high  water  mark. 

The  two  forms  of  turbines  may  be  illustrated  in  diagrams  (Figs.  27  and  28).    Fig.  27 

is  a  pressure  turbine  inward  flow,  with  guide  blades  so  as  to  give  direction  to  the  water 

and  regulate  the  quantity  ;  one  guide  blade  and  three  wheel  passages  are  shown  filled 

with  water.     The  water  under  pressure  enters  the  wheel  tangentially,  and  its  course  is 


RELATIVE  PATH  ABSOLUTE  PATH 

FIG.  28. — Diagram  of  Impulse  Turbine. 


Water  Turbines 


35 


reversed  in  the  passages  through  which  it  flows  and  falls  in  pressure,  so  that  when  it 
emerges  it  has  no  pressure. 

The  Jonval  type  of  turbine,  upon  which  system  so  many  pressure  turbines  are  made, 
is  shown  in  Fig.  29  as  a  diagram.  It  consists  of  a  ring  of  guide  blades  curved  to  guide 
the  water  into  a  ring  of  wheel  blades  curved  the  opposite  way.  The  water  presses 


FIG.  29. — Jonval's  Turbine. 


FIG.  30. — Impulse  Turbine. 


through  the  full  wheel  passages,  strikes  and  presses  against  the  wheel  blades,  losing 
its  pressure  in  driving  the  wheel. 

The  impulse  turbine  is  shown  in  diagram  (Fig.  28)  with  two  jets  full  and  two  wheel 
buckets  nearly  full.  Here  the  water  is  spurted  at  full  velocity  against  the  vanes  in  the 
wheel,  which  are  wide  enough  apart  to  allow  the  water  to  be  deviated  without  filling 


FIG.  31. — Impulse  Turbine.     Guide  Vanes 
and  Wheel  Blades. 


FIG.  32. — Fontaine  Turbine. 


the  buckets  ;  and  in  order  to  allow  the  water  to  spread  out  as  it  flows  through  the 
wheel,  the  vanes  are  splayed  out  towards  the  outfall  as  shown  in  the  cross  section 
in  Fig.  30.  The  guide  blades  and  buckets  are  shown  in  Fig.  31.  K  is  the  guide  blade, 
G  and  H  are  vent  holes  in  the  side  of  the  wheel  buckets  to  allow  air  to  escape  and  so 
prevent  back  pressure.  In  the  impulse  turbine  there  may  be  as  many  guide  blades  as 
buckets,  and  the  water  may  flow  full  bore 
all  round,  but  that  is  not  necessary  ;  there 
may  be  only  a  few  water  jets  on  a  large 
wheel,  in  which  case  it  is  called  a  partial 
flow  turbine. 

In  the  old  Fontaine  turbine,  shown  in  FlG  33._Blades  of  Fontaine  Turbine, 

part  section,  the  jets  could  be  closed  separ- 
ately by  sliding  gates,  as  shown  in  Fig.  32.  This  shows  in  the  two  partially  closed 
jets  that  the  water  does  not  flow  steadily,  but  is  broken  up  in  the  wheel,  and  so  its 
power  is  wasted.  Again,  in  the  full  flow  the  water  chokes  the  wheel  buckets  (Fig.  33), 
because  they  are  not  splayed  out  at  the  exit,  and  the  water  requires  pressure  to  force 
it  out. 


Modern  Engines 


In  Fig.  34  the  Girard  improvement  is  seen,  wherein  the  buckets  are  curved  and 
splayed  so  that  the  water  at  full  gate  never  fills  them,  but  leaves  an  open  ventilating 

space. 

In  these  impulse  turbines,  partially  closing 
the  jets  is  bad  regulation  ;  for  regulating  purposes 
the  active  jets  should  be  reduced  or  increased  in 
number  by  stopping  them  off  one  at  a  time. 

The  simplest  impulse  turbine  is  the  Pelton 
wheel,  driven  by  a  free  jet.  This  is  shown  in 
diagram  in  Fig.  35,  the  wheel  carrying  on  its  cir- 
cumference a  series  of  double  cupped  buckets  ;  the 
jet  at  full  velocity  due  to 


FIG.  34. — Girard  Turbine. 


strikes  the  mid-rib, 

splits  into  two,  and  glances  off  reversed  in  motion. 
Now,  in  reversing  it  exerts  a  great  pressure  on  the 
cups  delivering  up  its  momentum. 

In  choosing  a  turbine  we  must  be  guided  first 
by  the  condition  of  the  tail  race.  If  the  tail  water 
level  is  liable  to  considerable  variations,  then  a 
pressure  turbine  should  be  selected  to  work  either 
drowned  or  through  a  draught  tube.  But  the 
impulse  turbine  is  much  easier  regulated  where  water  supply  is  variable  and  none  too 
much  of  it. 

Again,  pressure  turbines  run  up  high  in  rotational  speed 
on  high  pressures,  while  impulse  turbines  can  be  made  with 
partial  flow  and  with  wheels  large  in  diameter,  so  that  with 
the  same  vane  speed  the  rotations  are  smaller. 

The  pressure  turbine  is  cheaper  than  the  impulse  on 
moderate  falls  with  lots  of  water,  but  for  the  higher  falls  the 
impulse  turbine,  like  the  Pelton  wheel,  is  cheaper  and  better. 

To  sum  up  the  features  of  the  two  classes.     The  impulse 
turbine  must  always  discharge  above  the  tail  water.     It  will 
work  with  complete  or  partial  flow  for  full  load.     Regulated  FlG.3S._PeltonWh~1Bucket. 
by  closing  one  or  more  guide  passages. 

The  pressure  turbine  discharges  either  below  tail  water  or  above  tail  water  through 
a  draught  tube.  It  is  regulated  by  closing  some  of  the  guide  passages  or  by  varying 
their  area  or  throttling  the  water  supply.  At  full  load  turbines 
are  all  highly  efficient,  some  as  high  as  85  per  cent.;  but  at  lower 
speeds  the  efficiency  falls  off  rapidly.  The  most  efficient  governor 
at  low  loads  is  that  applied  to  the  Vortex  pressure  turbine  (Fig. 
27),  where  the  inlet  to  the  wheel  vanes  is  closed  or  opened  by 
the  guide  blades  moved  by  a  governor. 

Here  the  impulse  turbine  has  the  advantage,  as  we  can  stop 
off  the  jets  without  causing  losses.  A  Girard  turbine  of  200 
horse-power  on  a  test  gave  an  efficiency  of  0.8  full  load  and  0.802 
on  half  load,  the  speed  the  same  in  both  cases. 

There  is  another  type  of  turbine,  not  much  used  but  of  some 
interest  scientifically,  as  it  illustrates  the  true  pressure  turbine. 

Two  nozzles  mounted  on  a  hollow  shaft,  and  pointing  tangen- 
FIG.  36.— Reaction  Wheel,  tially  as  shown  in  Fig.  36,  will  rotate  with  power  when  pressure 
water  is  supplied  through  the  shaft.     To  understand  this  turbine 

we  begin  with  the  knowledge  that  a  fluid  water  under  pressure  exerts  an  equal 
pressure  on  all  sides  of  a  containing  vessel.  Now,  if  we  remove  a  part  of  one 
side  of  a  containing  vessel  under  water  pressure  the  water  will  flow  out  of  the 


Water  Turbines 


37 


opening,  but  the  total  pressure  on  the  side  of  the  vessel  in  which  the  opening-  is 
made  will  be  so  much  less  than  the  pressure  on  the  opposite  side  by  the  area  of  the 
hole  multiplied  by  the  pressure.  Thus  if  the  vessel  had  four  sides  of  9  inches  area, 
and  out  of  one  side  we  cut  a  i  square  inch  hole  and  the  pressure  per  square  inch  is 
10  Ibs.,  then  on  the  side  out  of  which  the  inch  hole  is  cut  the  total  pressure  will  be 
8  x  10  =  80  Ibs.  on  that  side,  while  the  pressure  on  the  opposite  side  will  be  9  x  10  =  90  Ibs. 
A  difference  of  10  Ibs.  pushing  in  that  direction  would  move  the  vessel  away  opposite  to 
the  issuing  water.  And  to  obtain  efficiency  the  vessel  should  move  at  a  speed  at  least 
about  .8  \/2  gh. 

The  chief  point  to  observe  in  the  design  of  this  class  of  turbine  is  that  the  supply  of 
water  to  the  vessel  with  the  nozzle  or  hole  is  abundant  and  sufficient  to  maintain  the  full 
pressure  behind  the  hole.  And  if  the  water  is  to  pass  through  a  hollow  shaft  this  means 
a  very  large  shaft. 

But  this  can  be  overcome  and  a  good  construction  made  of  a  turbine  on  this 
principle.  At  the  speed  required  for  high  falls  the  water  in  the  wheel  acquires  an 
enormous  centrifugal  force,  and  the  friction  of  the  water  is  considerable.  By  making  a 
compound  wheel  this  speed  can  be  reduced  to  half.  It  is  of  importance  in  steam 
turbines,  this  modification  for  reducing  speed  without  loss  of  efficiency. 


TURBINES,  THEIR  CONSTRUCTION 

We  shall  now  take  up  each  class  of  turbine  with  a  view  to  examine  their  con- 
struction. In  the  preceding  division  we  have  only  considered  their  general  mode  of 
action  and  application.  When  one  comes 
to  consider  turbines  practically,  not  only 
is  the  direction  of  flow  axial,  or  radial  or 
mixed  flow  merely  a  matter  of  convenience, 
but  there  is  little  or  no  difference  in  action 
between  a  pressure  turbine  and  an  impulse 
turbine.  We  have  followed  this  classifi- 
cation so  far  because  it  is  the  usual 
text-book  classification.  In  the  following 
descriptions  we  shall  see  that  all  turbines 
work  by  reaction,  by  entering  a  wheel  in 
one  direction,  deviating  in  the  wheel,  and 
emerging  as  nearly  as  possible  in  the 
opposite  direction.  It  is  a  familiar  fact 
that  any  body,  solid  or  fluid,  moving  in 
any  direction  and  meeting  another  body 
which  intercepts  the  moving  one  and  re- 
verses its  movements,  experiences  a  pres- 
sure proportional  to  the  square  of  the 
speed  before  impact. 

In  this  respect  all  turbines  are  alike : 
the  water  must  be  deviated  by  the  wheel. 
And  so  we  best  can  select  a  starting-point  from  a  turbine  which  can  be  dissected  into 
either  pressure  or  impulse  wheels,  observe  the  deviation  of  the  water  and  the  produc- 
tion of  the  acting  pressures. 

All  turbines  can  be  developed  from  Barker's  mill,  the  original  form  of  which  is 
shown  in  Fig.  37,  and  which  was  merely  a  development  of  Hero's  steam  turbine 
invented  2000  years  before. 

Whitelaw  and  Stirrat,  in  Scotland,  made  a  special  study  of  this  wheel,  and  con- 
cluded that  the  arms  should  be  curved  into  an  Archimedean  spiral,  which  of  course 


FIG.  37. — Barker's  Mill. 


Modern  Engines 


would  finish  at  a  tangent  to  the  periphery,  as  shown  in  Fig.  38.  The  black  spiral  line 
is  the  curve  of  the  line  of  the  arm.  Whitelaw  found  that  the  arm  should  taper  from  the 
centre,  beginning  wide  and  gradually  narrowing  to  the  periphery  as  shown  in  the  left 
hand  curve,  but  later  tests  have  proved  that  the  opposite  curve,  widening  out  to  the 
periphery,  is  equally  as  good  and  more  efficient. 

The  two  forms  are  shown  better  in  Figs.  39  and  40,  which  show  one  with  the 
narrow  end  of  the  nozzle  outward  and  one  with  the  wide  end  outward.  Now,  an  inspec- 
tion will  show  the  difference  in  Fig.  40.  With  the  narrow  end  n  out  the  full  pressure 

will  be  continued  up  to  the  very  end,  and  the  jet  will  issue 
at  full  speed,  so  that  the  wheel  periphery  must  move  back 
with  a  speed  about  o.8*/2gh\  but  the  point  of  pressure 
pushing  the  wheel  back  is  down  at  b  near  the  line  F,  and 
the  pressure  acts  on  the  back  of  the  nozzle  at  P. 

Now,  in  the  other  case  (Fig.  40)  the  full  pressure  is  at 
line  F,  and  the  water  deviates  along  the  reversed  curve  all  the 
way,  and  the  pressure  is  distributed  along  the  curve  from  a 
to  b  gradually  without  the  water  touching  the  other  side  of 
the   nozzle  P.     Here  the  issue  of  the  water  from  the  narrow 
FIG.  38—Diagram  of  Curvature         t  jg  restricted  by  the  curve  a,  b,  and  its  outflow  is  at  a 
of  Arms  of  Reaction  Wheel.      f  ,      .  ./.     .  '      '.  , 

less  velocity  than  if  it  issued  direct  into  the  atmosphere  as 

in  the  first  case  ;  consequently  the  efficiency  is  higher.  Another  way  to  look  at  it  is  to 
consider,  in  the  first  case  the  centre  of  back  pressure  is  near  the  line  F,  while  the  centre 
of  back  pressure  in  the  second  case  is  midway  between  a  and  b,  farther  from  the  centre. 
Now,  if  we  cut  the  nozzles  across  at  the  line  F  and  fix  the  centre  piece  with  the 
one  inner  part  of  the  nozzle,  and  mount  the  outer  part  of  the  nozzles  on  a  rotatable 
shaft,  Fig.  39  would  exactly  represent  pressure  turbine  guide  blades  and  vanes,  in  which 
the  pressure  would  be  due  to  reaction  in  b.  And  Fig.  40  would  exactly  represent  the 
guide  blades  and  wheel  vanes  of  an  impulse  turbine. 


FlG.  39. — Wheel  with  Narrow-Mouthed  Nozzle. 


FIG.  40. — Wheel  with  Wide-Mouthed  Nozzle. 


In  the  first  case  the  water  fills  the  nozzle  at  full  pressure,  and  it  escapes  at  full 
velocity,  the  centre  of  back  pressure  being  at  b. 

In  the  second  case  the  water  enters  the  cut-off  nozzle  at  n  at  full  velocity  without 
pressure,  glides  along  the  curve,  and  falls  off  with  little  or  no  velocity.  The  centre  of 
back  pressure  is  half-way  between  a  and  b. 

In  this  Hero  form  of  turbine,  then,  we  see  that  a  very  simple  alteration  in  the  guide 
and  exit  passages  makes  all  the  difference  between  a  pressure  and  an  impulse  turbine, 
and  that  the  guide  blades  are  not  necessarily  fixtures. 

Now  again,  if  we  take  the  form  (Fig.  40)  in  which  the  water  issues  from  the  nozzle 


Water  Turbines 


39 


at  full  velocity,  and  mount  another  wheel  free  to  move  in  the  opposite  direction  to  the 
reaction  wheel  inside,  as  shown  in  Fig.  41,  both  wheels  would  revolve  in  opposite 
directions,  the  inner  being  a  pressure  turbine  and  the  outer  an  impulse  turbine. 


FIG.  41. — Combined  Pressure 
and  Impulse  Turbine. 


FIG.  42. — Hydraulic  Experiment. 


In  this  turbine  the  two  opposite  revolving  wheels  are  geared  to  one  horizontal  shaft 
by  3  bevel  wheels. 

We  are  now  prepared  to  consider  the  various  types  as  constructed,  but  first  we  shall 
note  the  usual  forms  and  facts  regarding  water  and  the  hydraulic  formulae. 

Atmospheric  pressure  is  roughly  estimated  at  14.7  Ibs.   per  square  inch,  with  a 
3O-inch  barometric  height.     And  the  column  of  water  this  can 
support  in  a  water  barometer  is  34  feet. 

Let  H  represent  head  of  water,  in  this  case  the  head  is 

34  feet;  hence 


14.7 
inch  ;  or,  pressure  = 


=2.3  feet  head=i  Ib.  pressure  per  square 

^  =  0.432  Ibs.  per  foot-head. 
34 


A  cubic  foot  of  water  weighs  62.5  Ibs.  if  fresh,  and  64  Ibs. 
if  sea  water. 

Let  P  =  pressure  per  square  foot,  H  height  of  column, 
A  its  area  in  square  feet,  and  W  the  weight  of  water  per 


FIG.  43. — Hydraulic 
Experiment. 


cubic  foot;  then  PA  =  WHA,  and  P  =  WH,  and  H  =  . 


These  show  the  connection 


between  head  and  pressure.    Thus  if  we  connect  a  long  vertical  pipe  C  to  a  water  supply 
main  B  the  water  will  rise  to  a  height  H  (Fig.  42),  due  to  pressure  P. 

Now,  as  to  velocity,  if  water  issues  from  a  converging  nozzle  (Fig.  44)  on  a  vessel 


FlG.  44. — Hydraulic  Experiment. 


FIG.  45. — Hydraulic  Experiment. 


as  in  Fig.  43,  we  can  imagine  a  single  drop  of  water  of  weight  W  falling  from  the 
surface  to  the  orifice.     When  on  the  top  at  rest  it   has  potential  energy  WH,   but 

WV2  WV2 

on  falling  it  has  acquired  kinetic  energy  = ,  so  that  WH  =  — —  ,  and  V  = 

or  approximately  =  8 


4° 


Modern   Engines 


The  conversion  of  head  pressure  and  velocity  is  shown  very  well  by  Froude's 
experiments  shown  in  Fig.  45.  If  a  pipe  of  varying-  bore  is  attached  to  a  water 
vessel,  and  small  vertical  pipes  are  attached  to  the  discharge  pipe  at  the  different 
bores,  the  water  will  rise  in  these  small  pipes  and  indicate  the  side  pressure  at  the 
different  points.  As  the  same  quantity  of  water  passes  each  section  of  the  pipe  the 
velocity  of  the  flow  is  inversely  as  the  section,  and  the  pressure  inversely  as  the 
velocity ;  hence  the  indicator  pipes  show  the  difference  in  pressure  by  the  height  of 
water.  If  this  difference  of  height  between  the  level  of  the  water  in  the  tank  and  the 

V2 
pipes  is  measured  it  will  be  found  to  be  equal  in  each  case  to  H  =  —  ,  where  H  is  the 

2S 
difference  between  the  pipe  levels  and  tank  level. 

Thomson's  water  jet  pump  (Fig.  46)  is  sometimes  explained  on  the  hypothesis  that 
the  high  pressure  jet  acquires  such  a  velocity  on  discharging  at  the  nozzle  that  the 
pressure  falls  below  that  of  the  atmosphere,  but  the  experiments  of  Siemens  on  steam 


FIG.  46. — Thomson's  Water  Jet  Pump. 

jet  pumps  and  others  prove  that  friction  between  the  high  velocity  jet  and  the  air  carries 
off  the  air  with  the  jet,  and  thus  produces  a  partial  vacuum  behind  the  nozzle.  This 
raises  the  water  until  the  two  streams  meet,  one  at  high  velocity  of  small  section  and 
the  other  of  large  section  and  small  velocity.  The  velocity  of  the  one  is  decreased  by 
expending  its  energy  in  increasing  the  velocity  of  the  other  larger  stream  sufficient  to 
discharge  the  larger  body  of  water  through  a  pipe  widening  towards  the  outlet,  at  a 
higher  level  than  that  from  which  it  is  drawn. 

The  same  action  takes  place  in  the  locomotive,  where  the  blast  pipe  carries  by  its 
high  velocity  jet  of  steam  a  large  stream  of  air  and  gas  at  a  slower  velocity  out  against 
the  atmospheric  pressure.  This  jet  effect  will  be  further  referred  to  under  steam  power. 

When  water  flows  from  a  reservoir  from  a  pipe  B  to  a  lower  level  n,  and  discharges 
through  an  orifice  of  very  small  size  compared  with  the  pipe,  the  whole  head  is  practi- 
cally applied  to  the  orifice,  as  the  velocity  in  the  pipe  may  be  so  small  as  to  be  neglected  ; 
but  if  the  discharge  is  comparatively  large  (Fig.  47),  or  the  orifice  area  a  large  fraction 
of  the  pipe  section,  then  the  whole  head  is  expended  in  the,  three  forms  of  H  due  to 

P  V2 

head  of  unexpended  fall — T^due  to  pressure,  and—    due  to  velocity,  and  multiplying 

o 

each  by  W  gives  the  energy  in  each  form  ;  and  in  i  ib.  of  water  the  total  would  be 

P       V2 

E  =  H  +  ^  H at  the  discharge. 

W     2 


Water  Power  41 

The  turbines  to  be  considered  act  either  by  one  or  two  or  all  three  of  these  forms 
of  energy.  In  the  impulse  turbine  and  jet  turbine,  like  the  Girard  and  Pelton  wheel,  we 
want  the  full  velocity  at  the  jet ;  hence  the  fall  pipe  must  be  large  enough  in  area  to 
reduce  the  velocity  in  the  pipe  to  a  negligible  quantity,  so  that  the  full  pressure  due  to 
head  is  at  the  orifice  of  the  jet,  and  not  expended  in  the  pipe. 

In  the  pressure  turbine  we  require  the  water  delivered  to  the  turbine  under  pressure, 
so  that  as  the  water  passes  through  the  wheel  it  losses  its  momentum  in  a  forward 
direction.  If  V  is  the  forward  component  of  the  entering  velocity,  each  Ib.  of  water 

changes  its  momentum  =  —  ;  hence  —  gives  the  forward  pressure  on  the  wheel  due  to 

&  & 

each  Ib.  of  water  per  second.     If  Vl  is  the  velocity  of  the  wheel    at  the  entrance  of 

the  water,  the  work  per  Ib.  of  water  will  be  = 1  foot-lbs.  per  second. 

g 
And  as  the  energy  given  by  i  Ib.  of  water  at  head  H  is  H  foot-lbs. ,  of  which  a  large 

fraction  is  given  to  the  wheel,  .•.  H= 1,  the  energy  equation  for  turbines. 

o 

The  guide  blades  are  curved  to  give  a  large  forward  velocity.  Practically,  the 
velocity  in  pressure  turbines  at  the  entrance  to  the  wheel  is  half  that  due  to  the  head, 
and  the  pressure  half  that  due  to  the  head. 

The  quantity  of  water  theoretically  discharged  by  an  orifice  is  the  product  of 
velocity  V  and  the  area  ejf  the  orifice  A.  Cubic  feet  per  second  =  Q  =  AV,  and 
V  =  8  */H  .'.  Q  =  8A  ^/H.  But  owing  to  friction  this,  in  practice,  is  reduced  by  0.96. 


FIG.  47. — Hydraulic  Experiment. 

In  practice  we  take  the  effective  head  at  the  wheel  by  a  pressure  gauge,  as  no 
coefficient  can  be  given  for  loss  due  to  pipe  resistances.  Again,  we  need  not  trouble 
about  the  discharge  through  thin  plates  or  peculiar  tubes  in  this  place.  In  all 
turbines  the  orifices  are  shaped  as  near  as  possible  to  the  form  of  a  converging 
nozzle,  so  that  the  area  of  the  orifice  is  equal  to  the  area  of  the  water  jet.  Allowances 
must  also  be  made  for  friction  and  bends  in  pipes,  all  of  which  are  rather  beyond  our 
present  scope. 

Momentum  of  water,  as  we  have  seen  above,  is  the  important  factor  in  turbine 
power.  In  theoretical  mechanics  the  unit  of  force  is  i  Ib.,  and  of  mass  32.2  Ibs.  =g, 

W 

or  mass  =  — 

g  V 

Velocity  V  is  feet  per  second.     Vt=  feet  x  seconds.     -  =/=  acceleration  which  is  the 

increase  of  V  in  each  second.     If  any  force  is  constant  the   acceleration  is  uniform. 
This  force  being   measured   by  the   increase   of  momentum   it  produces.     Momentum 

w  wv 

=  mass  x  velocity,  and  hence  force  producing  acceleration  =  -r/J  also  P/  =  —_ ,  and  if 

f>  G» 

P    is    pressure    and    t    time  =  i    second,    W   weight   of  water    flowing    per    second, 

^X  =  change  of  momentum,  and  P  = =  change  of  momentum. 

To  apply  these  formula?  to  turbines  we  must  take  only  useful  cases. 


42  Modern   Engines 

ist  case,  the  Pelton  wheel  bucket  or  cup.  The  velocity  of  the  jet  is  Vx,  and  of  the 
bucket  forward  is  V2.  When  the  jet  strikes  the  relative  velocity  is  V:  -  V2  forward, 
and  when  the  jet  is  turned  back  Vl  —  V2  backward. 

The  absolute  velocity  of  the  jet  is  Vx  before  it  strikes,  and  after  V2—  (Vx  —  V2)  = 
2V2-V1  weight  of  water  per  second  is  WACVj  —  V2)  ;  therefore  the  pressure  on  the 

,.„              f                       WArVi-VjjJV,     WA(V1-V2)(2V2-V1)       WA,W      ..  x, 
cup  =  difference  of  momentum  = i— 1 91 — 1  = L_i 2/v 2 y  _  2 — A(V,  -  V9)2. 

?  ff  g. 

From  this  it  is  easy  to  deduce  that  if  V2  =  |V1  the  absolute  velocity  of  rejected  water 

is  o,  and  all  the  energy  of  the  water  given  up  to  the  wheel. 
In  all  cases  impulse  pressure  on  the  turbine  blades  is 

=  momentum  before  entering  -  momentum  on  exit. 

In  pressure  turbines  it  is  =  (momentum  +  pressure)  —  (momentum  +  pressure)  before 
and  after  passage  through  the  wheel. 

In  the  Hero  reaction  wheel  momentum  is  of  no  account  whatever,  unless  the  outlets 
are  curved  to  form  impulse  wheel  blades  ;  then  in  that  case  we  get  the  back  pressure 
= /A  4- the  momentum  of  the  fluid  entering  the  curved  exit -the  momentum  on  leaving 
the  curved  exit.  But  as  it  is  difficult  to  shape  the  orifice  so  as  to  change  the  momentum 
entirely  in  its  passage  it  is  necessary,  in  using  reaction  wheels,  to  compound  them  with 
an  ordinary  impulse  wheel,  so  that  the  remaining  energy  in  the  jet  is  absorbed  by  this 
additional  wheel.  This  is  more  important  with  wheels  driven  by  steam,  air,  or  gas 
pressure,  wherein  the  fluid  velocity  is  very  high,  and  we  shall  deal  with  this  under 
steam  turbines. 

In  the  practical  construction  of  turbines  all  these  principles  are  applied,  and  upon 
them  the  dimensions  of  the  parts  of  the  turbine  are  calculated  for  the  best  effects. 

We  shall  now  consider  the  practical  turbines  of  present  day  manufacture.  The 
simple  Pelton  wheel  has  proved  the  best  for  high  falls  under  most  circumstances,  and 
we  may  begin  with  that  turbine.  It  is  not  to  be  supposed  that  it  was  designed  by  its 
inventor  on  scientific  knowledge  that  the  pressure  was  greatest  on  the  cups  when 
V2  =  ^V1,  or  that  completely  turning  back  the  jet  gave  twice  the  pressure,  which  he 
obtained  by  striking  the  jet  on  the  old  flat  board  vanes  of  the  primitive  wheel, — the 
miner's  "hurdy-gurdy  wheel," — which  was  built  in  ignorance  of  all  hydraulic  laws, 
yet  it  did  good  work,  and  probably  had  an  efficiency  of  40  per  cent.  Its  great  advantage, 
however,  was  that  it  could  be  made  on  the  spot  from  the  timber  at  hand,  rough  and 
readily  put  up. 

An  interesting  paper,  read  before  the  American  Institute  of  Mining  Engineers  by  W. 
A.  Doble,  may  be  consulted  on  this  wheel,  from  which  the  following  details  are  obtained. 
It  seems  that  the  double  cup  with  the  mid-rib  was  invented  by  several  engineers, 
but  Mr.  Pelton  certainly  has  the  credit  of  introducing  it. 

Mr.  Pelton's  own  account  of  his  invention  is  interesting.  It  appears  that  one  of 
the  cup-shaped  wheels  already  mentioned  got  loose  on  its  shaft,  and,  being  displaced 
relatively  to  the  jet,  the  latter  struck  the  side  instead  of  the  centre  of  the  bucket.  It 
was  observed  that  under  these  conditions  the  mill  which  the 
wheel  was  driving  ran  faster.  As,  however,  the  eccentric  position 
of  the  jet  caused  an  end  thrust  on  the  shaft,  Mr.  Pelton  pro- 
posed first  to  have  two  sets  of  buckets  mounted  on  either  side 
of  the  wheel,  the  side  thrust  on  the  one  set  of  buckets  being 

pIG<  4g Pelton  Wheel     counterpoised   by   that   on    the    other,    the  jet    playing    on    the 

dividing  line  between  the  two  sets  of  buckets,  as  indicated  in 

Fig.  48,  for  which  we  are  indebted  to  Mr.  Doble's  paper.  The  step  from  this 
arrangement  to  the  splitting  wedge  was  obvious,  and  was  made  by  Mr.  Pelton,  a 
mid-section  through  whose  bucket  is  shown  in  Fig.  50,  whilst  Fig.  49  shows  a  com- 
plete bucket  in  perspective.  This  type  of  bucket  soon  came  into  general  use,  and 
with  it  the  claim  for  very  high  running  efficiencies.  How  far  these  claims  are  sub- 


Pelton  Wheels 


43 


stantiated  is  even  yet  a  matter  of  dispute,  the  results  obtained  in  different  careful 
experiments  varying  through  very  wide  limits.  The  highest  figure  which  seems  at  all 
well  authenticated  is  one  of  91.85  per  cent.,  which  is  said  to  have  been  attained  in  the 
case  of  a  26-inch  cascade  wheel  tested  by  Professor  Hitchcock  in  the  engineering 
laboratory  of  the  Ohio  State  University  in  1897.  This  figure  was  obtained  with  a  head 
of  163  feet ;  the  flow  of  water  was  2085  Ibs.  per  minute,  and  the  bucket  velocity  46.2 
feet  per  second.  The  wheel  ran  at  447  revolutions  per  minute,  and  gave  35  horse-power 
on  the  brake.  A  similar  wheel  of  larger  size,  giving  80  brake  horse-power,  showed  an 
efficiency  of  90.04  per  cent.  In  the  absence  of  complete  details  as  to  the  method  of 
conducting  the  test  these  figures  will  be  treated  with  some  reserve,  and  perhaps  the 
same  should  be  said  as  to  certain  tests  made  by  Mr.  Ross  E.  Browne  in  the  laboratories 
of  the  University  of  California  in  the  year  1890.  Here  a  Pelton  wheel  15  inches  in 
diameter,  working  with  a  T7^-inch  nozzle  under  a  head  of  50  feet,  is  stated  to  have 
shown  an  efficiency  of  82.6  per  cent.,  whilst  with  a  jj-inch  nozzle  the  efficiency  was 
82.5  per  cent.  On  reducing  the  head  to  8  feet  the  efficiency  was  73  per  cent.  On  the 
other  hand,  in  some  experiments  made  in  1897  at  the  M'Gill  University,  by  Mr.  J.  T. 
Farmer,  the  wheel  made  a  much  less  favourable  showing,  the  highest  efficiency  recorded 
being  70  per  cent.  The  wheel  tested  in  this  case  was  a  Pelton  No.  3  motor,  18  inches 
in  diameter.  The  experiments  were  made  with  heads  up  to  235  feet,  and  with  nozzles 


FIG.  49.— Pelton's  Bucket.     FIG.  50.— Section  of  Pelton's  Bucket.  FlG.  51.— Section  of  Berry's  Bucket. 


i-inch  and  f-inch  in  diameter,  whilst  the  speed  was  varied  both  above  and  below  the 
point  of  maximum  efficiency,  which,  as  stated,  was  but  70  per  cent.  This,  no  doubt, 
is  a  very  fair  result,  but  is  far  below  those  claimed  in  the  tests  made  by  Professor 
Hitchcock  and  Mr.  Browne.  If  the  figures  obtained  by  these  observers  can  be  accepted, 
it  would  seem  that  there  is  practically  no  margin  left  for  any  substantial  improve- 
ment in  the  tangential  water  wheel.  Nevertheless,  as  commonly  constructed,  there 
are  several  possible  causes  of  dissipation  of  energy.  In  the  first  place,  the  angle  at 
which  the  jet  strikes  the  bucket  varies  as  the  wheel  turns  round,  whereas  in  a  well 
constructed  impulse  turbine  this  angle  is  constant,  and  is,  moreover,  more  nearly 
tangential  to  the  direction  of  the  jet  than  is  the  case  with  the  bucket  of  a  tangential 
wheel. 

Further,  as  often  constructed,  the  flat  lower  lip  of  the  bucket  slaps  the  jet  instead 
of  entering  it  quietly.  This  defect  has  probably  arisen  from  the  makers  neglecting  to 
take  into  account  the  relative  motion  of  the  bucket  and  of  the  jet.  A  type  of  bucket 
patented  by  Mr.  S.  L.  Berry,  Philadelphia,  has  no  lower  lip  at  all,  but  is  brought  to 
a  sharp  edge.  The  back  of  this  entering  lip  is  bevelled  away  so  that  it  will  stand 
clear  of  the  jet  throughout  its  motion.  The  jet-splitting  wedge  is  curved  in  the 
vertical  plane.  This  curve  is  chosen  so  that  the  vertical  angle  between  the  jet  and 
the  wedge  changes  little  throughout  the  action  of  the  jet.  This  curve  is  easily 
drawn  by  determining  the  virtual  direction  of  the  jet  at  three  points  in  the  path  of 


44 


Modern   Engines 


the   bucket  and  drawing-  a   circle   through   these.      As  shown  in  Fig.  51,   the  jet   on 
leaving  the  wheel   does  so  in  the  direction  of  cd,  thus  clearing  the  next  bucket ;    it 

carries  away  with  it,  therefore,  residual  energy 
due  to  the  transverse  velocity  bd.  It  will  be 
seen  that  in  order  that  this  should  be  small 
it  is  necessary  that  the  buckets  of  a  tangential 
water  wheel  should  not  be  too  closely  spaced, 
as  otherwise  the  jet  on  leaving  one  bucket  will 


FIG.  52.— Doble's  Bucket.     Plan. 


FlG.  53. — Doble's  Bucket.     Sectional  Elevation. 


FIG.  54. — Doble's  Bucket.     Elevation. 


strike  on  the  back  of  the  next.     The  bucket  just  described  would  seem  to  have  several 
points   of  superiority  as  compared  with  the  ordinary  Pelton   bucket.     The    latter    in 

another  way  also  violates  hydrodynamic  principles, 
since  it  is  a  maxim  in  hydraulics  to  avoid  any  kind 
of  sharp  corner  or  angle  to  which  the  flowing  water 
may  have  access.  In  Fig.  49  it  will  be  seen  that 
there  are  a  number  of  sharp  corners  in  the  bucket. 
It  is  true  that  the  bulk  of  the  water  will  avoid  these, 
but  since  a  jet  striking  a  surface  at  an  angle  spreads 
in  all  directions,  some  water  must  find  its  way  into 
these  corners,  and  some  loss  by  eddying-  must  thereby 
arise.  A  bucket  which  appears  to  have  special  merits 
in  this  regard  is  the  Doble  ellipsoidal  bucket,  which  is 
illustrated  in  Figs.  52  to  55.  In  this  bucket  the  lower  edge  is,  it  will  be  seen,  cut  away 
near  its  centre,  and  the  jet-splitting  wedge  E  terminates  in  a  sharp  point  F,  which 
will  enter  the  jet  as  the  bucket  comes  round  with  a  minimum  of 
disturbance.  Whatever  direction  the  water  may  flow  in,  it  meets 
a  surface  of  easy  curvature,  and  is  delivered  over  the  edges  of  the 
bucket  with  a  proper  residual  velocity.  We  have  no  particulars  as 
to  the  absolute  efficiency  attained  with  wheels  thus  fitted,  but  they 
have  been  used  to  replace  other  buckets  on  the  wheels  of  the 
San  Joaquin  Electric  Company,  with  an  increase,  it  is  stated,  of 
12  per  cent,  in  efficiency.  This  statement  may,  of  course,  mean 
much  or  little,  dependent  upon  the  efficiency  of  the  wheels  in 
their  original  state ;  but  theoretical  considerations,  as  already 
mentioned,  would  lead  us  to  anticipate  that  the  Doble  buckets 
should  prove  exceedingly  good  whenever  they  are  submitted  to  a  r ., 
properly  conducted  test.  Another  feature  claimed  for  them  is  that 
they  wear  very  uniformly  when  the  water  supply  is  charged  with 
sand.  Thus  in  the  Mount  Whitney  Power  Company's  plant, 
although  the  working  head  is  1300  feet,  and  no  sand  traps  were 
originally  fitted,  the  wheel  was  still  in  excellent  condition  at  the  end  of  fifteen  months. 


FIG.  55. — Doble's 
Bucket.     End  View. 


45 


FIG.  56.— Type  of  Pelton  Wheel. 


After  this  a  sand  trap  was  brought  into  use,  and  it  was  found  that  the  water,  though 

clear,  was  highly  charged  with  granite  sand.     A  pit  100  feet  long  by  6  feet  wide  fills  up 

4  feet  in  from  three  to  five  days,  so  that  during  its  15  months'  work  the  buckets  must 

have  been  subjected  to  the  scour  of  500  or  600  cubic  feet  of  sand  per  day.      As  the 

velocity  of  the  jet  is  about  295  feet  per  second  it  is  only  natural  that  the  buckets  were 

somewhat  worn  ;  but  this  wear  has  been  uni- 
formly  distributed,    and   the    surfaces    are    as 

smooth  and  perfect  as  when  originally  fitted. 

One  of  these  turbines  is  illustrated  in  Fig.  56. 

The  wheels  are  4  feet  in  mean  diameter,  and 

are   designed   to   run   at    250   revolutions   per 

minute.     The   most   usual    plan   of  governing 

wheels    of   the   Pelton   kind   has   in   the   past 

been  that  of  simply  deflecting  the  jet,  so  that 

it  failed  to' strike  the  buckets.     This  plan  is, 

of  course,  wasteful   ot  water,  since   as   much 

is  sent  into  the  tail  race  when  the  wheel  is 

running  light  as  when  loaded,  and  in  practice 

is    less    simple   to    carry   out    than    might    at 

first   sight   appear.      In   short,    the    nozzle   is 

mounted  on  a  ball-and-socket  joint,  such  as  is  used  with  hydraulic  mining  monitors. 

This  joint  has  to  be  kept  tight  under  high   pressures,  and   yet   it   must  nevertheless 

move  easily  when  necessary,   if  "hunting"  is   to  be   avoided   and  the   speed   of  the 

wheel  kept  fairly  constant.     The  difficulties  in  effecting  this  led  to  the  very  ingenious 

system  of  governing  by  Cassel. 

In  this  case  (Fig.  57)  the  wheel  is  built  up  of  two  discs  mounted  on  the  same  shaft, 

along  which  they  are  free  to  slide,  but  are 
normally  held  in  contact  with  each  other  by 
springs.  Each  disc  carries  a  series  of  half 
Pelton  buckets  as  shown.  So  long  as  the  two 
half  buckets  are  in  contact  the  wheel  acts  as 
an  ordinary  Pelton  wheel.  The  discs,  however, 
are  provided  with  weighted  levers  so  arranged 
that  under  the  action  of  the  centrifugal  forces 
developed  on  the  rotation  of  the  wheel  the  two 
discs  are  forced  apart  as  indicated  in  Fig.  57,  so 
soon  as  the  speed  rises  above  a  certain  pre- 
determined limit.  The  jet  then  passes  between 
the  wheels  and  is  wasted  in  the  tail  race.  With 
this  arrangement  the  wheel  is  its  own  governor, 
and  accordingly  the  control  of  speed  is  remark- 
ably prompt  and  efficient. 

The  plan  of  reducing  the  pressure  pro- 
ducing flow  through  the  nozzle  by  means  of 
a  throttle  valve  has  also  been  tried,  but  is 
objectionable,  in  that  the  speed  of  the  jet  is 
thereby  reduced  and  the  water  no  longer  enters 

the   wheel   without   shock,    a   waste   of  energy   thus   arising.      A   simple   plan,   which 

we  can  well   believe   gives  very  good   results,   is  described  and  illustrated  in  Fig.  58. 
In  this  case  a  sharp  edged   sluice  is,   it  will  be  seen,  fitted   before   each   nozzle,  and 

the  wheel  is  governed  by  moving  this  sluice  so  as  to  cover  more  or  less  of  the  opening. 

This  method  affects  the  velocity  of  the  jet  very  little,  but  changes  its  shape,  and  there 
may  therefore  be  some  loss  from  splashing,  owing  to  the  inversion  of  the  jet.     As  is 


FlG.  57. — Type  of  Pelton  Wheel. 


Modern  Engines 


FIG.  58. — Sluice  Governors  of  Pelton  Wheel. 


well  known,  to  be  stable  a  jet  must  be  circular  in  section.     If  of  any  other  form  the 
surface  tension  tends  to  bring  it  to  this  form,  but  overdoes  the  correction,  so  that  in 

point  of  fact  the  shape  of  the  jet 
oscillates  about  the  circular  sec- 
tion. It  is  quite  probable  that  with 
heads  of  fair  weight  the  velocity 
of  the  jet  will  be  too  great  for  any 
action  of  this  kind  to  have  any 
perceptible  effect  in  the  passage 
between  the  jet  and  the  buckets. 
Mr.  Doble's  arrangement  is  of 
the  throttling  type,  but  the  details 
of  the  construction  are  such  that 
a  solid  cylindrical  jet  is  obtained, 
issuing  at  practically  constant 
velocity  at  all  gates,  from  full  bore 
down  to  under  one-fifth  full  bore. 
The  throttle  piece  is  pear  shaped, 
and  is  maintained  central  with  the  jet  by  being  mounted  on  a  cylindrical  rod  passing 
through  the  back  of  the  casing,  and  which  can  be  moved  in  or  out.  The  water  issues 
through  the  annular  space  between  the 
throttle  piece  and  the  jet.  The  outer  end 
of  this  throttle  piece  projects  always  through 
the  orifice  of  the  jet,  and  terminates  in  a 
fine  point  connected  by  easy  curves  with  the 
thickest  portion  of  the  body.  The  water 
clings  to  these  curves,  so  that  the  jet  is 
always  cylindrical  and  solid.  Figs.  60  and 
61  show  the  jet  obtained  with  various  open- 
ings of  the  nozzle.  The  steadiness  and  trans- 
parency of  the  jet  is  remarkable  (Fig.  59). 

Nearly  all  tangential  wheels  act  much  in 
the  same  way  as  this  Pelton  wheel.  The 
Girard  turbines  being  much  the  same  in 
principle,  although  very  different  in  construc- 
tion, in  both  the  momentum  of  the  jets  is 
converted  into  pressure  on  the  wheel  cups  or 
blades  in  being  arrested  and  turned  back  in 
its  motion  ;  and  while  the  angular  velocity 
of  the  wheel  at  the  wheel  blades  is  necessarily  about  half  the  linear  velocity  of  the  jet, 
the  revolutions  of  the  wheel  may  be  chosen  and  arranged  for  by  calculating  the  diameter 
necessary  to  obtain  the  angular  velocity  at  the  given  speed,  and  from  this  the  radius,  or 


FIG.  59. — Jet  from  Doble's  Nozzle. 


FIG.  60. — Jet  from  Doble's  Nozzle.     Full  open. 

one  of  the  radii  r  of  the  wheel,  may  always  be  found  ;  thus  in  a  wheel  like  Pelton's  r  is 
the  radius  from  centre  of  shaft  to  centre  of  cups.  Suppose  that  half  the  velocity  of 
the  jet  is  30  feet  per  second,  and  the  wheel  limited  to  10  revolutions  per  second,  then 


Outward  Flow  Turbine 


47 


-? —  =  3  feet  as  the  circumference  at  radius  /-.  the  centre  of  the  buckets  from  which  r 

10  revs. 

is  found. 

In  the  outward  radial  flow  (Girard)  there  are  the  inner  radius  rand  the  outer  r2 ; 
and  having  found  r,  r2  is  found  by  k  x  r,  wherein  k  is  a  constant  about  =  1. 17  to  1.18. 


FIG.  61. — Jet  from  Doble's  Nozzle.     Partially  open. 


THE  GIRARD  TURBINE 

This  is  an  impulse  turbine  in  which  the  wheel  buckets  are  not  under  pressure,  but 
may  be  a  full  or  partial  flow  wheel. 

It  is  made  in  various  forms,  like  all  other  turbines.  Thus  for  high  falls  it  can  be 
placed  at  the  bottom  of  a  wheel 
pit  and  the  water  led  down  by  a 
pipe,  so  that  it  enters  either  be- 
tween twin  wheels  or  under  one 
wheel,  and  supports  the  weight 
of  the  wheel  and  shaft,  as  in  the 
case  of  Niagara  Falls. 

And,  again,  for  high  falls 
where  slow  rotation  is  desired  it 
can  be  made  a  partial  flow  wheel, 
so  that  although  the  rotations  are 
low  the  peripheral  speed  is  still 
high  enough  for  good  efficiency. 

Fig.  62  represents  Messrs. 
Gunther's  turbine  of  the  class  for 
deep  wheel  pits.  When  a  turbine 
is  placed  in  a  deep  pit,  and  the 
upright  shaft  is  of  extreme  length 
and  of  great  weight,  it  may  be 
desirable  to  reduce  the  load  on 
the  footstep  as  much  as  possible, 
and  in  such  cases  a  Girard  tur- 
bine of  special  design  with  radial 
outflow  is  adopted.  In  this  type 
the  water  enters  the  turbine  from 
the  underside,  is  admitted  on  the 

inner  circumference  of  the  wheel,  and  is  discharged  radially  outwards ;  the  water 
pressure  thus  exerts  thrust  on  the  wheel,  and  the  footstep  has  only  to  carry  the  weight 
of  the  moving  parts. 

Fig.  63  is  from  a  photo  of  one  of  two  radial  Girard  turbines  driving  a  large  textile 
mill  abroad,  each  wheel  being  63  inches  internal  diameter,  and  of  525  horse-power,  with 
95  feet  fall ;  the  two  turbines  drive  by  steel  bevel  wheels  on  to  the  same  second  motion 
shaft,  and  each  upright  shaft  is  about  80  feet  long. 


FIG.  62. — Girard  Turbine  lor  Deep  Wheel  Pits. 


48 


Modern   Engines 


The  two  diagrams,  Figs.  64  and  65,  show  the  construction  of  the  partial  flow  turbine 
of  this  type.  G  is  the  inlet  nozzle,  furnished  at  its  nose  with  two  or  more  guide  blades 
movable  by  rack  and  pinion  for  regulating  purposes.  It  will  be  seen  from  this  that  the 
wheel's  diameter  is  independent  of  the  velocity  of  water  flow. 


FlG.  63. — Girard  Turbine  with  Radial  Outflow. 

For  this  class  of  turbine  we  will  take  a  partial  flow  example  with  a  high  fall,  and 
not  a  great  quantity  of  water.     Let  us  take — 
h  as  the  head  in  feet  =  400. 

Q  the  quantity  of  water  available  in  cubic  feet  =  4  per  second. 
R  =  500  the  limit  of  revolutions  of  the  shaft  per  minute. 


Outward   Flow  Turbines 

A  is  the  area  of  the  guide  passages. 

Ag  the  area  of  the  wheel  passages  at  entrance  or  inner  radius. 

r  is  the  outer  radius  wheel. 


49 


r<>  the  inner  radius  of  the  wheel. 


C  the  velocity  of  the  inner  radius  in  feet  per  second. 
C2  velocity  of  the  outer  radius  in  feet  per  second. 
V  the  velocity  of  water  issuing  from  guide  passages. 
V2  velocity  of  water  from  wheel. 
Then  V  =  o.94x8>/A   (i). 


,  , 


" 


L2  =  y  x  i. 08,  as  the  wheel  blades  must  never  be  filled. 

}  =  C  (found  by  taking  the  revolutions  per  second) -i-R  (in  this  case  52?  =  8.?), 

60 

— and  dividing  C  by  this  number  =— ,  the  product  will  give  the  cir- 

R 

cumference  of  the  inner  r2,  from  which  r  can  be  found. 


FlG.  64. — Section  of  Girard  Turbine. 
Beginning    with    C,    we    find    that   C  = 


FIG.  65. — Section  of  Girard  Turbine. 
0.94  x  8  *J h  _  0.94  x  8  V4oo      0.94  x  8  x  20 


=  -£-  feet  =  75  feet  per  second  ;  and  the  value  of  r2  =  --  =      -  =  9  feet  as  circumference 
of  r2,  from  which  we  get  easily  1.5  feet  as  the  radius  of  rz. 

The   area   of  the   guide    blade   passages   is  =  A  =  ^=  -4— =  0.0266  square   feet,  or 

nearly  3!  square  inches. 

Area  of  wheel  passages  A2  =  Ax  i.o8=3.75x  1.08  =  4  square  inches. 

The  circumference  9  feet,  found  above,  would  be  the  inner  circumference,  and  for 
the  purpose  of  calculating  the  axial  breadth  of  the  wheel  blades  we  must  find  the 
number  of  blades  required. 

The  guide  blade  passages  A  =  3. 75  square  inches;  and  if  we  divide  this  between 

three  orifices  in  the  nose  ot  the  guide  each  would  be  3-75  _  1>2g  square  inches  area, 

3 

say  i^  x  i ;  i£  inches  axially  and  i  inch  measured  circumferentially. 
VOL.  i. — 4 


5° 


Modern  Engines 


The  wheel  blades  passages  are  somewhat  larger  =  4  inches,  and  axially  they  would  be 
the  same  as  the  guide  blades,  i^  inches  ;   and  if  we  divide  the  4  inches  into  3  we   get 

4=1.33  inches  as  the  width  between  the  blades  on  the  wheel  at  the  inner  radius  r  in 

3 

inches;  we  must  add  to  this  the  thickness  of  the  blades.     In  a  wheel  of  this  high  velocity 

for  a  small  quantity  of  water  it  would  be  made  as  light  in  weight  as  possible  and  well 

balanced.     The  blades  would  be  no  more  than  £  inch  thick,  hence  from  centre  of  one 

blade  to  centre  of  next  would  be  =  1.33 +0.125  =  1.455  inches  ;  and  this  into  108  inches, 

the  circumference  =  -^ —  =  74  blades. 

1-455 

If  the  guide  nozzle  had  only  one  orifice  of  3.75  square  inches  we  could  alter  the 
wheel  blade  design  considerably;    thus   the   wheel  orifice,   being   4   inches,    could   be 

divided  into  two  of  2  x  2  inches,  and  the  nozzle,   one  orifice,  ?i75_  1.875  inches  and 
2  inches  axially  measured.      This  would  give  2.125  from  centre  of  one  blade  to  the 


next  on  the  circumference ;  hence 


1 08 
2.115 


=  50  blades. 


FIG.  66. — Girard  Turbine  Complete. 


Fig.  64  illustrates  the  sections 
of  the  wheel  and  guide  blades  and 
passages,  and  Fig.  65  the  orifices, 
nozzles,  methods  of  regulation  by 
a  sliding  sluice  worked  by  rack  and 
pinion. 

The  blades  are  splayed  out,  as 
formerly  explained,  to  enable  the 
water  to  spread  as  it  passes  through 
the  passages,  so  that  the  outer  area 
of  the  passages  is  somewhat  greater 
than  their  inner  passages. 

The  outer  radius  r  should  be  to 
r2  as  1.18  is  to  i.  In  this  case  rz  is 
1 8  inches  ;  hence  r=  1.18  x  18  =  21^, 
and  the  buckets  would  therefore  be 
3^  inches  radially. 

The  efficiencyis  about  75  per  cent. 

at  best,  so  that  as  the  power  =  ^ '-?,  0  =  240  cubic  feet  per  minute,  and  h  =  400,  62.5 

33,000  .. 

240  x  400  x  62. 5       ,  ,  , 

the  weight  of  one  cubic  foot,  hence  0.75  — 5  =  about  130  actual  horse-power. 

33,000 

There  is  no  pressure  between  the  guide  blades  and  the  wheel,  and  as  the  water 
enters  the  buckets  without  pressure  it  is  freely  deviated  by  them,  and  takes  a  course 
quite  independent  of  their  shape.  The  action  of  the  water  on  the  wheel  depends  on 
the  angle  through  which  each  particle  is  deviated  whilst  freely  flowing  over  the  buckets, 
and  as  these  latter  are  not  full  there  is  no  disturbance  of  the  action  as  they  pass  in  front 
of,  or  away  from,  the  jets. 

The  turbine  illustrated  in  Fig.  66  is  shown  with  part  of  the  hood  removed,  which 
prevents  the  water  from  flying  about.  The  water  enters  through  the  valve  shown  at  the 
left-hand  side  of  the  Figure,  and  passes  directly  into  a  distributing  chamber,  from  which 
it  jets  on  to  the  buckets  of  the  wheel  through  gates  or  ports,  varying  in  number 
according  to  circumstances.  When  there  is  only  one  port  it  can  be  reduced  in  size 
when  water  is  scarce  or  less  power  required  ;  and  when,  as  is  frequently  the  case,  there 
are  many  ports,  a  sufficient  number  of  them  may  be  used  to  suit  the  requirements  of  the 
moment.  The  arrangement  by  which  the  power  is  regulated  is  easily  worked  either 
by  hand  or  by  a  governor. 


Water  Turbines 


THE  VORTEX  WHEEL 

These  are  inward  flow  turbines  with  fixed  guide  blades,  and  include  the  Thomson 
vortex  wheel  with  a  few  movable  guide  blades  for  regulating  the  quantity  of  water 
and  power. 

This  vortex  turbine  has  much  to  recommend  it.  The  regulation  is  easy  and 
certain,  due  to  the  balancing  of  the  inward 
pressure  by  the  outward  pressure,  due  to 
centrifugal  force.  In  fact,  it  will  interest 
electricians  to  study  this  turbine,  as  it  is  a 
hydraulic  illustration  of  the  electromotor,  and 
both  act  upon  the  same  fundamental  mechan- 
ical law.  This  turbine,  when  supplied  with 
water  under  pressure,  acts  as  a  motor  and 
gives  off  power,  but  at  the  same  time  it  acts 
as  a  centrifugal  pump,  and  hence  produces  a 
counter  pressure,  and  it  works  at  its  greatest 
activity  when  the  counter  pressure  is  half  the 
working  pressure.  A  pump  is  a  water  pres- 
sure generator,  a  turbine  is  a  water  pressure 
motor,  a  dynamo  is  an  electric  pressure  gener- 
ator, an  electric  motor  is  an  electric  pressure 
motor.  The  vortex  and  other  inward  radial 

flow  turbines  act  in  both  capacities  when  at 

i         T     .LI.        i  FIG.  67. — Turbine  at  Niaeara  Falls. 

work.     In  the  electromotor  a  counter  pressure 

is  generated  in  the  same  way,  and  the  greatest  activity  is  also  obtained  when  the 
•counter  pressure  is  half  the  working  pressure,  but  its  efficiency  is  greater  the  nearer 
the  counter  pressure  approaches  the  value  of  the  working  pressure. 

In  considering  this  fact  tne  author  advocates  the  inward  flow  radial  type  of  turbine 
for  single  expansion  steam  turbines,  in  which  the  counter  pressure  would  moderate  the 
-steam  flow.  However,  that  is  for  another  chapter. 

We  shall  enter  fully  into  the  consideration  of  this  type 
of  turbine,  for  with  this,  the  Pelton  wheel,  and  improved 
Jonvals  all  cases  can  be  met. 

The  turbine  selected  for  illustration  is  the  Gilke's 
vortex,  and  after  fully  describing  it  we  shall  calculate  its 
dimensions.  When  these  are  correct  and  the  speed 
adjusted  to  the  number  of  revolutions  necessary  to  give 
the  counter  pressure  about  half  the  working  pressure,  it 
runs  with  great  smoothness  and  silently. 

Referring  to  the  fundamental  turbine,  the  Hero  reaction 
wheel,  this  vortex  wheel  can  be  traced  back  to  that  also  ; 
for  it  would  work  even  if  the  guide  blades  were  fixed  to  the 
wheel  blades  and  rotated  with  them  ;  in  fact,  it  works  well 
so  made.  This  is  shown  in  Fig.  68. 

In  fact,  all  pressure  turbines  can  be  traced  to  this 
simple  form  of  wheel,  and  by  starting  from  that  ancestor  we  could  treat  them  as 
reaction  wheels,  from  the  size  of  the  orifices  at  the  outlet,  and  the  pressure  of  water 
in  the  wheel,  and  the  centre  of  pressure. 

Let  us  for  a  time  depart  from  the  orthodox  treatment  of  pressure  turbines,  and 
consider  them  from  another  point  of  view.  Turbines  have  been  very  thoroughly 
investigated,  and  the  results  of  practice  have  been  carefully  and  accurately  compiled, 


FIG.  68. — Turbine  with  Rotating 
Guide  Blades. 


Modern  Engines 


so  that  new  views,  while  they  may  not  advance  the  theory  much,  may,  however, 
have  some  practical  results  ;  indeed,  they  have  already  had  practical  results  of  value. 
In  further  developing-  the  fundamental  turbine,  suppose  we  make  a  wheel  as  in  Fig-. 
67,  the  inner  curved  part  of  the  blades  B  would,  in  an  inward  flow  turbine,  be 
fixed,  and  the  inner  reverse  curves,  the  wheel,  movable.  In  this  case  (Fig.  68), 
however,  they  are  one  blade  and  move  together,  the  pressure  water  entering  on  the 
inner  periphery  and  flowing1  out  at  the  outer  A  into  the  exhaust.  We  could  calculate 
the  power  by  the  pressure  difference  between  the  one  side  of  the  passage  and  the 
other  due  to  the  unopposed  pressure  opposite  the  exit  of  the  passages,  just  as  we 
could  in  a  Barker's  mill.  In  this  case  the  inner  orifices  have  a  larger  area  than  the 
outer  ones,  otherwise  there  would  be  no  pressure  in  the  passages  ;  we  make  it 
an  outward  flow  wheel  by  a  slight  alteration,  wherein  the  orifices  on  the  outer 
periphery  are  contracted,  and  the  inner  ones  opened  out  to  admit  the  water  pressure. 
Here  we  have  the  genesis  of  the  outer  and  inward  flow  pressure  turbines  called  reaction 
turbines.  First,  it  is  observable  that  the  inward  flow  has  the  advantage,  in  that  it  is 


End  View,  with  Front  Cover  Removed. 


Sectional  Elevation. 


FIG.  69. — Inward  Flow  Turbine. 

natural  that  the  inner  orifices  should  be  the  smaller  on  the  small  circumference,  and  the 
large  orifices  on  the  outer  radius  freely  admit  the  water. 

Let  us  see  what  teaching  there  is  in  this  theory.  First,  to  revert  back  to  the 
reaction  wheel  in  its  simple  form,  to  maintain  the  pressure  in  this  turbine  the  inlet  must 
be  large  compared  with  the  outlet  nozzles  in  sectional  area,  in  order  that  the  pressure 
of  the  water  be  maintained  in  the  wheel  opposite  the  exit,  so  as  to  get  the  back  driving 
pressure.  The  exits  at  B  in  the  inward  flow  turbine  would  then  be  small  compared  with 
the  entrances  at  A,  and  the  full  pressure  due  to  the  head  would  be  maintained  in  the 
wheel  passages,  and  the  pressure  being  high  would  tend  to  cause  great  leakage  past 
the  sides  of  the  wheel  into  B.  But  that  can  be  overcome  mechanically,  as  in  the 
ordinary  vortex  wheel.  A  wheel  on  this  principle  is  shown  in  Fig.  69,  an  end  view  and 
sectional  elevation.  The  fluid  enters  at  H  and  fills  chamber  A  at  full  pressure  ;  it  enters 
wheel  C  by  wide  orifices  on  the  outer  radius,  and  is  deviated  tangentially  and  discharged 
through  smaller  nozzles  or  orifices  in  the  inner  radius,  from  which  it  is  exhausted 
through  E.  These  are  diagrammatic  figures  of  actual  turbines  ;  the  entrances  to 
the  wheel  passages  are  curved  so  as  to  save  friction  and  eddy  currents.  Now,  it  is 
evident  that  in  this  turbine  only  pressure  is  at  work,  and  very  little  of  that  pressure  is 
due  to  momentum. 


Water  Turbines  53 

The  nearest  approach  to  it  in  action  is  the  vortex  wheel,  in  which  reaction  is  due 
to  half  pressure  and  half  momentum,  and  by  altering  this  wheel  so  that  its  outlets  are 
very  small  compared  with  its  inlets,  it  can  be  made  also  to  work  with  small  momentum 
and  large  pressure  in  the  wheel  passages. 

The  chief  advantage  and  only  raison  cP&tre  for  the  use  of  guide  blades  in  pressure 
turbines  of  reaction  type  is  to  convert  the  pressure  of  the  water  into  momentum  in  the 
guide  passages,  so  that  the  pressure  is  small  at  the  clearance  between  the  two  sets  of 
blades,  which  must  be  of  some  width,  and  not  subjected  to  high  pressure  to  cause  great 
leakage.  The  guide  blades  restrict  the  inflow  of  water,  and  as  it  finds  little  resistance 
owing  to  the  outer  or  inner  discharge  orifices  being  nearly  as  wide  as  the  inlets,  i.e. 
the  guide  passages,  it  rushes  through  at  high  velocity  across  the  clearance  space  into 
the  wheel  passages  ;  here  it  is  arrested  and  its  momentum  reconverted  into  pressure, 
and  is  discharged  in  the  opposite  direction  from  the  orifices.  This,  then,  is  the  object 
of  fixed  guide  blades,  to  reduce  the  pressure  by  converting  it  into  velocity,  so  that  the 
pressure  is  relieved  from  the  exit  of  the  guide  blades  and  the  inlet  of  the  wheel  passages, 
enabling  the  water  to  jump  from  one  to  the  other  at  high  velocity  and  with  little  side 
pressures  tending  to  leakages. 

Fig.  67  is  a  part  section  ot  the  pressure  turbines  at  Niagara  Power  Generating 
station,  showing  the  shape  of  blades  and  passages  very  well,  and  they  are  certainly  of 
correct  form  for  fixed  and  movable  blades.  But  the  same  turbines  could  be  altered  to 
work  without  guide  blades  ;  this  I  have  shown  in  Fig.  68. 

In  both  cases  the  pressure  water  would  enter  from  the  inside  for  mechanical  reasons, 
and  discharges  into  the  atmosphere.  In  the  turbine  with  fixed  blades  (Fig.  67)  there 
are  three  conversions  of  energy :  first,  the  potential  energy  of  the  fall  is  converted  into 
kinetic  energy  in  the  guide  blades,  and  each  particle  is  for  an  instant  arrested  in  the  wheel, 
where  its  kinetic  energy  is  converted  into  pressure,  which  again  is  converted  into  velocity 
with  which  the  water  escapes.  Under  these  conditions  the  velocity  of  the  wheel  blades 

should  be  — ,  where  V  is  the  velocity  of  the  water  as  it  jumps  the  clearance  space, — this 
2 

in  order  to  use  the  momentum  to  best  advantage. 

In  the  case  of  the  wheel  with  no  fixed  blades  there  is  only  one  conversion  of  energy. 
The  potential  energy  of  the  water  is  converted  into  kinetic  energy  by  the  difference  of 
pressure  caused  by  the  unopposed  pressure  opposite  the  orifice  moving  the  wheel  round. 
Theoretically,  the  best  speed  would  be  that  due  to  the  head  of  water,  so  that  the  outer 
radius  should  have  an  angular  velocity  =  V  =  8  -Jh  nearly  in  this  turbine. 

The  question  between  the  two  is,  then,  whether  the  guide  blades  fixed  are  better  and 
cheaper  than  the  packing  devices  required  to  prevent  leakages  of  water  in  a  wheel 
without  them. 

The  vortex  wheel  shows  that  the  packing  is  no  difficulty,  and  its  four  large  guide 
blades  might,  if  it  were  not  for  their  excellent  regulating  functions,  be  discarded  by 
curving  the  wheel  blades  differently,  as  shown  in  Fig.  68. 

The  reason  why  in  all  turbines  so  much  depends  upon  the  angles  and  curves  of  the 
blade  is  simply  due  to  the  velocity  of  the  water  passing,  and  its  inertia,  and  momentum. 
It  must  be  diverted  and  have  its  motion  altered  in  direction  gradually,  and  pass  from 
the  guides  to  the  wheel  without  striking  a  sudden  blow  or  shock. 

From  these  few  observations  the  student  will  gather  the  different  views  on  the 
theories,  and  their  discussion  is  interesting.  We  will  now  proceed  with  the  discussion 
of  the  reaction  pressure  turbine,  the  vortex  wheel. 

In  pressure  turbines  the  buckets  of  the  wheel  must  be  completely  filled  with 
water  (as  otherwise  there  would  be  no  pressure),  and  consequently  the  turbine  must 
receive  the  water  all  over  the  circumference  in  order  to  act  efficiently.  If  this  be  not 
done  one  of  two  actions  takes  place  according  as  the  turbine  be  working  submerged  or 
not.  If  the  turbine  be  submerged  the  buckets,  after  leaving  the  guide  blade  orifices, 


54 


Modern  Engines 


are  full  of  still  water,  which  has  to  be  displaced  when  they  come  round  to  the  orifices 
again.      Hence    in   each    revolution    a   considerable    amount    of   power    is    wasted    in 

imparting  momentum  to  the 
mass  of  water  carried  round 
in  the  wheel.  If  the  turbine 
be  not  submerged  a  con- 
siderable quantity  of  water 
is  used  in  filling  the  buckets 
(which  have  become  empty 
on  leaving  the  guide  blade 
orifices)  before  the  full  pres- 
sure at  the  circumference 
can  be  utilised.  It  is  not 
easy  to  find  a  mode  of  re- 
gulating pressure  turbines 
which  does  not  involve 
shutting  the  water  off  part 
of  the  circumference  (so 
making  them  partial  ad- 
mission turbines)  or  other- 
wise greatly  affecting  the 
conditions  of  the  admission 
of  the  water.  The  vortex 
turbine  is  only  affected  by 
back  water  to  the  extent 

FIG.  70. -Vortex  Turbine.  that    the     water    level    is 

affected.  It  can  be  placed 
above  the  bottom  of  the 
fall,  so  that  part  of  the  head 
can  be  utilised  by  suction. 
And  in  many  cases  it  is 
the  cheapest  form  of  tur- 
bine to  adopt. 

The  principles  of  the 
vortex  and  the  mode  in 
which  the  water  is  applied 
in  it  will  be  readily  under- 
stood by  reference  to  Figs. 
70  and  71. 

Fig.  71  shows  the  in- 
ternal arrangement  of  the 
vortex.  The  water  enters 
the  outside  casing  at  the 
top, — or  in  any  other  posi- 
tion that  may  be  conven- 
ient,— and  passing  thence 
is  directed  by  four  (or  more) 
guide  blades  on  to  the  outer 
circumference  of  the  re- 
volving wheel,  which  is 
driven  round  at  a  velocity 
depending  on  the  height  of 
the  fall.  The  water,  having  FIG.  71.— Vortex  Turbine  with  Cover  Removed. 


Vortex  Turbines  55 


expended  its  energy  in  giving  motion  to  the  wheel,  is  discharged  through  the  two 
central  openings,  half  the  amount  being  carried  away  by  each  suction  pipe.  The  guide 
blades,  it  will  be  noticed,  are  movable,  and  turn  about  on  a  pivot  placed  near  their 
inner  ends.  The  method  in  which  these  guides  are  simultaneously  regulated  will  be 
seen  by  reference  to  Fig.  70,  which  is  an  outside  view  of  the  same  turbine. 

The  power  is  obtained  with  a  slower  velocity  of  water  than  in  ordinary  turbines. 
This  is  effected  by  the  balancing  of  the  centrifugal  force  of  the  water  in  the  revolving 
wheel  against  the  pressure  due  to  half  the  head,  so  that  only  one-half  of  the  fall  or  head 
is  employed  in  giving  velocity  to  the  water,  the  other  half  acting  simply  in  the  condition 
of  fluid  pressure.  Hence  the  velocity  of  the  water  in  no  part  of  its  course  exceeds  that 
due  to  one-half  of  the  fall,  and  the  loss  from  fluid  friction  and  agitation  of  the  water  is 
thus  materially  less  than  in  other  turbines  where  the  water  is  required  to  act  at  much 
higher  velocities. 

From  the  principle  of  injection  of  the  water  from  without  towards  the  centre, 
which  is  adopted  in  the  vortex,  there  results  another  saving  of  effect,  since  it  admits 
of  the  use  of  long  and  well  formed  channels  by  which  the  water  is  made  gradually  and 
regularly  to  converge  in  passing  from  the  outer  chamber,  where  it  is  comparatively  at 
rest,  to  the  point  of  entrance  to  the  wheel  chamber,  where  its  velocity  should  be  greatest. 
The  advantage  of  such  convergent  channels  for  the  transmission  of  water  with  a 
minimum  of  loss  of  effect,  as  compared  with  short  passages  such  as  are  generally 
employed  in  other  turbines,  is  well  known. 

Further,  from  the  same  principle  of  injection  towards  the  centre  there  is  an 
accordance  between  the  velocities  of  all  parts  of  the  moving  wheel  and  the  proper 
velocities  of  the  water  in  its  passage  between  the  points  of  entrance  and  discharge. 

The  water  when  it  has  its  greatest  velocity  is  admitted  to  the  circumference  of  the 
wheel,  which  is  the  most  rapidly  moving  part,  and  when  it  has  as  far  as  possible 
imparted  its  power  to  the  wheel  it  leaves  at  the  centre,  which  has  the  least  motion. 

The  water  enters  from  the  guide  passages  with  the  velocity  at  which  the  outer 
circumference  of  the  wheel  is  moving  and  without  change  of  direction,  so  there  is  no  loss 
from  impact. 

The  steadiness  and  regularity  of  the  motion  of  the  vortex  are  remarkable,  conse- 
quent upon  the  action  of  the  centrifugal  force  of  the  water,  which  on  any  increase  in  the 
velocity  of  the  revolving  wheel,  increases  and  so  checks  the  supply  entering  from 
the  guide  passages,  and  on  any  diminution  of  the  velocity  of  the  wheel,  diminishes  and 
admits  the  water  more  freely,  thus  counteracting  in  degree  the  irregularities  of  speed 
arising  from  variations  in  the  work  to  be  performed.  With  other  turbines  and  ordinary 
water  wheels  the  variation  in  speed,  when  the  amount  of  work  or  resistance  to  the 
motion  varies,  frequently  is  a  source  of  great  inconvenience. 

Besides  the  adaptations  referred  to,  which  combine  to  give  the  vortex  a  great 
superiority  in  efficiency,  it  possesses  another  advantage,  which  is  in  many  situations  of 
the  highest  importance,  namely,  the  simple  and  excellent  mode  of  adjustment  to  varying 
supplies  of  water  by  means  of  the  movable  guide  blades. 

The  guide  blades,  as  already  mentioned,  are  made  movable  upon  gudgeons  or 
centres  near  their  points,  motion  being  imparted  to  them  simultaneously  by  a  hand  wheel, 
which  can  be  placed  in  any  position  easily  accessible.  By  a  very  slight  motion  of  the 
guide  blades  the  orifices  may  be  contracted  at  pleasure,  and  are  thus  made  to  suit  any 
quantity  of  water  which  it  may  be  necessary  or  desirable  to  use  ;  and  it  will  be  seen  that, 
to  whatever  extent  these  are  open,  the  following  important  conditions  of  efficient 
application  of  the  water  are  fulfilled : — 

i  st.   The  channels  are  of  a  gradually  convergent  form. 

2nd.  The  water  is  uninterrupted  in  its  course,  and  enters  the  wheel  chamber  from 
the  narrowest  part  of  the  channels,  and  consequently  attains  its  maximum  velocity  at 
the  point  of  application. 


Modern  Engines 


up 


FIG.  72. — Vortex  Turbine  Wheel. 


3rd.  The  water  is  admitted  equally  to  the  whole  circumference  of  the  wheel. 
Fig.  72    is   taken   from   a   photograph   of  a   vortex   wheel   with   the   outer   cover 
removed  to  illustrate  the  form  of  the  vanes.     Some  of  these  do  not  extend  to  the 
central  orifice  ;    the  object  in  so  making  them  is  that  they  may  not  too  much  fill 
the  contracted  part  of  the  passages  and  thus  impede  the  flow  of  the  water. 

The  wheels  (Fig.  73)  are  constructed  either  of  steel  or  of  rolled  brass  (the  latter 
for  small  sizes),  and  as  the  vanes  can  thus  be  made  very  much  thinner  than  of  cast  metal 

their  number  can  be  increased,  and  perfect 
accuracy  in  the  curvature  secured.  Hence  the 
water  enters  the  wheel  with  less  interruption 
and  passes  through  more  exactly  in  the  direc- 
tion intended  than  is  the  case  where  the  vanes 
are  of  greater  thickness  and  fewer  in  number. 

The  vanes  are  fixed  on  each  side  of  a  steel 
or  brass  plate,  which  has  a  boss  in  the  centre 
to  secure  it  upon  the  shaft,  and  there  are 
two  outer  discs  or  covers  in  which  are  left 
circular  openings  through  which  the  water 
passes  after  it  has  done  its  work  ;  thus  one- 
half  of  the  water  is  discharged  on  each  side  of 
the  wheel. 

A  separate  movable  cover  is  placed  over 
the  wheel,  so  that  access  to  it  can  be  had 
without  disturbing  the  exterior  casing.  A 
cover  is  also  placed  over  the  guide  blade 
chamber  in  the  larger  wheels,  by  means  of 
which  access  can  be  obtained  to  every  part  without  moving  the  foundations  or  heavier 
portions  of  the  case. 

The  double  vortex,  with  movable  guide  blades,  should  be  adopted  on  all  medium 
and  high  falls  in  cases  in  which  the  amount  of  power  employed  varies  considerably  at 
different  times  ;  and  the  saving  of  water  is  important,  so  that  it  is  necessary  to  use  as 
small  a  quantity  as  possible  to  do  the  work  required  ;  or  when  the  available  supply  of 
water  is  at  times  less  than  the  full  amount  for  which  the  turbine  is  designed.  The 
consumption  of  water  can  then  be  economised  to  the  utmost,  as  the  passages  can  be 
regulated  to  admit  only  the  exact 
quantity  needed  to  do  the  work  or  to 
suit  the  available  supply. 

The  governing  of  turbines  is  in 
many  cases  more  difficult  than  the 
governing  of  steam  engines,  the  two 
chief  difficulties  to  be  overcome  being 
the  weight  of  the  moving  parts  and 
the  fact  that  if  the  guides  or  sluice 
by  which  the  governing  is  effected  are 

worked  too  quickly  very  considerable  hydraulic  shock  takes  place,  which  may  do 
damage  to  the  pipe  line.  There  are  many  governors  in  the  market ;  most  of  these  will 
give  fair  results  to  prevent  racing,  that  is  to  say,  they  will  not  allow  the  turbine  to  run 
away  so  much  as  to  do  damage  to  ordinary  machinery,  but  where  great  regularity  of  speed 
is  required  under  varying  loads, — for  example,  where  a  dynamo  is  supplying  the  electric 
current  direct  on  to  lamps  which  are  switched  in  or  out  from  time  to  time, — it  is  necessary 
to  provide  a  sensitive  governor  which  will  not  admit  of  perceptible  fluctuations  in  speed. 
Our  experience  of  Mr.  Murray's  hydraulic  governor  enables  us  cordially  to 
recommend  its  adoption  for  electric  lighting  plants  such  as  are  alluded  to  above,  or 


FIG.  73. — Vortex  Turbine  Wheels. 


Vortex  Turbines 


57 


for  any  other  purpose  in  which  extreme  steadiness  is  essential.  With  this  governing 
apparatus — a  full  description  of  which  will 
be  found  below,  the  water  is,  by  the  action 
of  a  high  speed  governor,  turned  to  one  end 
or  the  other  of  a  hydraulic  cylinder  which 
works  the  guide  blades.  Such  a  governor 
will  be  seen  in  Fig.  74,  Nos.  i  and  2  being 
sections  at  right  angles  to  one  another  of 
a  4-way  valve  forming  a  part  of  the  appar- 
atus, and  No.  3  an  elevation  showing  the 
complete  arrangement.  In  Nos.  i  and  2 
the  outer  casing  A  is  provided  with  a  supply 
port  B,  an  escape  port  C,  and  other  ports 
D  and  E  leading  respectively  to  the  top 
and  bottom  of  a  regulating  cylinder  which 
controls  the  supply  to  the  motor.  The  action 
of  the  apparatus  may  be  seen  from  No.  3, 
in  which  1  is  a  centrifugal  spring  governor 
driven  from  the  turbine  and  connected  by 
the  rod  J  with  a  lever  K,  to  which  the 
piston  H  is  connected  by  a  link.  When  the 
turbine  speed  increases  the  piston  is  raised 
and  water  passes  by  pipe  D  to  the  upper 
part  of  the  regulating  cylinder  L,  and  acts  on  a  piston  M  to  reduce  the  supply.  Should 


1" 


FIG.  74. — Murray's  Governor. 


FlG.  75. — Method  of  Fixing-  Vortex  Turbine, 
the  speed  decrease  the  water  passes  by  pipe  E  to  the  lower  part  of  the  cylinder  L  and 


Modern  Engines 


raises  the  piston,  and  permits  more  water  to  enter  the  turbine  so  as  to  maintain  normal 
speed. 

The  essential  difference  between  the  single  and  double  vortex  turbines  is  that  in  the 
former  the  water  is  only  discharged  from  one  side  of  the  wheel ;  the  wheel  of  the  single 
vortex  being,  in  fact,  half  of  that  of  the  double,  the  centre  plate  of  the  latter  forming  the 
top  cover  of  the  former. 

The  guide  blades  direct  the  water  on  the  wheel  in  precisely  the  same  manner  as  they 
do  in  the  double  vortex,  and  may  be  either  fixed  or  movable  as  is  desired. 

This  single  vortex  turbine  is  very  well  suited  to  medium  and  low  falls,  where  a 
considerable  body  of  water  is  to  be  dealt  with,  and  where  it  is  desirable  to  have  the 
turbine  left  dry  when  the  head  water  is  shut  off. 

As  the  water  is  only  discharged  below  the  wheel,  and  not  above  and  below  as  in  the 
double  vortex,  part  of  the  fall  may  be  utilised  by  a  suction  pipe. 

When  difficulty  or  expense  is  apprehended  in  sinking  the  foundations  a  considerable 


FIG.  76. — Vortex  Turbine  Direct  Coupled  to  Dynamo. 


saving  may  be  expected,  as  the  turbine  can  be  placed  on  a  platform  above  the  tail  water, 
and  no  work  need  be  done  below  the  water  level  beyond  the  sinking  of  a  hole  for  the 
suction  pipe  to  discharge  into. 

The  single  vortex  is,  of  course,  only  to  be  used  when  the  wheel  is  placed  horizontally 
with  a  vertical  spindle. 

It  will  be  seen  from  the  illustrations  that  the  heavy  cast-iron  casing  that  is  required 
for  the  double  vortex  is  dispensed  with. 

The  usual  method  of  fixing  the  single  vortex  is  shown  in  Fig.  75.  The  wheel  is 
placed  on  a  floor  made  of  timber  or  metal  in  a  pit  of  masonry  or  brickwork.  The 
timber  breasting  (which  for  convenience  is  shown  broken  away  in  the  engraving)  is 
of  the  same  height  as  the  sides  of  the  watercourse.  There  is  no  way  for  the  water 
to  pass  from  the  chamber  above  the  floor  to  the  tail  race  below  except  through  the 
turbine. 

The  diameter  of  the  single  vortex  is  naturally  larger  than  that  of  a  double  vortex 
for  the  same  power  ;  but  so  great  are  the  advantages  of  dispensing  with  the  outer  casing 
and  keeping  the  turbine  above  the  tail  water  level  that,  where  the  quantity  of  water  is 
large  and  fall  low,  it  is  adopted. 

As  the  wheels  are  comparatively  small  in  diameter,  the  rotational  speed  is  pretty 
high.  The  speed  of  the  wheel  is  some  large  fraction  of  the  speed  ot  the  water  as  it 
would  flow  out  ot  the  wheel  were  it  held  stationary  ;  and  being  closed  all  watertight, 


Vortex  Turbines 


59 


it  can  very  readily  be  coupled  to  a  dynamo  direct,  and  a  great  many  of  these  vortex 
turbines  are  so  used.     Fig1.  76  represents  one  of  small  size  so  adapted. 

Below  we  give  some  particulars  of  interest  regarding  the  single  vortex  wheel, 
from  which  the  quantity  of  water  required,  the  speed,  and  diameter  of  guide  blade 
channel  can  be  obtained. 

TABLE   IV. 


FALL  IN  FEET. 

H.P. 

8 

9 

10 

ii 

12 

[ 

Cubic  feet  per  minute       .... 

883 

784 

706 

642 

588 

10  ' 

Revolutions  per  minute   .... 

91 

106 

118 

128 

137 

1 

Approximate  weight  (cwts.)    . 
Diameter  of  guide  blade  channel  (inches) 

53 
63 

47 
61 

43 
59 

4i 

58 

39 

57 

( 

Cubic  feet  per  minute       .... 

J325 

1176 

1059 

962 

883 

iJ 

Revolutions  per  minute   .... 

80 

89 

99 

107 

118 

5  I 

Approximate  weight  (cwts.  )    . 

63 

59 

55 

53 

49 

I 

Diameter  of  guide  blade  channel  (inches) 

6? 

.       66 

64 

63 

61 

( 

Cubic  feet  per  minute      .... 

1765 

1470 

1412 

1284 

1176 

Revolutions  per  minute   .... 

7i 

83 

89 

96 

1  06 

20J 

Approximate  weight  (cwts.)    . 

73 

65 

63 

61 

57 

I 

Diameter  of  guide  blade  channel  (inches) 

73 

68 

67 

66 

65 

The  particulars  for  double  vortex  wheels  with  horizontal  shaft  are- 

TABLE  V. 


FALL  IN  FEET. 

H.P. 

36 

38 

40 

45 

So 

55 

60 

"1 

Diameter  of  inlet  (inches) 
Cubic  feet  per  minute 

IO 

118 

9 
106 

8 
88 

8 

76 

66 

7 
59 

7 

53 

1 

Revolutions  per  minute    . 

810 

960 

1055 

"37 

1389 

1474 

'553 

r 

Diameter  of  inlet  (inches) 

ii 

ti 

IO 

9 

8 

8 

8 

20\ 

Cubic  feet  per  minute 

157 

141 

118 

IOI 

88 

78 

71 

( 

Revolutions  per  minute   . 

768 

810 

936 

"37 

1216 

1290 

1359 

( 

Diameter  of  inlet  (inches) 

12 

12 

ii 

IO 

9 

9 

8 

25 

Cubic  feet  per  minute 

196 

I76 

147 

126 

no 

98 

88 

I 

Revolutions  per  minute   . 

730 

769 

886 

ion 

1216 

1290 

1359 

, 

Diameter  of  inlet  (inches) 

13 

13 

12 

ii 

10 

IO 

9 

3O-{ 

Cubic  feet  per  minute 

235 

212 

I76 

151 

132 

118 

106 

I 

Revolutions  per  minute   . 

644 

680 

842 

958 

1080 

1290 

1359 

f 

Diameter  of  inlet  (inches) 

15 

IS 

13 

13 

12 

ii 

n 

40 

Cubic  feet  per  minute 

282 

235 

202 

I76 

r57 

141 

( 

Revolutions  per  minute   . 

595 

629 

744 

910 

IO24 

1086 

"44 

f 

Diameter  of  inlet  (inches) 

17 

16 

15 

H 

13 

12 

12 

H 

Cubic  icet  per  minute 

392 

353 

294 

252 

221 

196 

I76 

1 

Revolutions  per  minute    . 

592 

629 

744 

803 

973 

1932 

1087 

6o 


Modern  Engines 


TABLE  \T .—continued. 


H.P. 

FALL  IN  FEET. 

36 

38 

40 

45 

50 

55 

60 

6oj 

Diameter  of  inlet  (inches) 
Cubic  feet  per  minute 
Revolutions  per  minute    . 

47° 

522 

18 
424 
549 

16 

353 
683 

VO  CO  CO 

H  Q  O 

COCO 

264 
859 

13 
235 
1032 

13 

212 

1087 

7°j 

Diameter  of  inlet  (inches) 
Cubic  feet  per  minute 
Revolutions  per  minute    . 

20 

549 
476 

19 

494 
502 

18 
412 
602 

16 

353 
737 

15 
3°Q 

788 

15 
275 
910 

00 

,{ 

Diameter  of  inlet  (inches) 
Cubic  feet  per  minute 
Revolutions  per  minute    . 

22 
628 
476 

21 

564 

502 

19 
47° 
549 

17 
404 
649 

16 
353 
695 

837 

'5 
282 
882 

IOOX 

Diameter  of  inlet  (inches) 
Cubic  feet  per  minute 
Revolutions  per  minute    . 

24 
784 

398 

23 
706 
462 

21 

588 
505 

19 
5°4 
580 

18 
441 
635 

392 
673 

16 

353 
706 

The  following  construction  is  used  in  setting  out  the  blades  in  an  inward  radial 
flow  turbine. 

The  guide  and  wheel  blades  for  inward  flow  turbines  are  partly  involutes  of  a  circle, 

to  lessen  the  contraction  of  the  stream  as  it 
flows  through  the  passages.  Fig.  760,  A  is 
the  external  circumference  of  the  guide  ap- 
paratus, and  B  the  internal  circumference ; 
draw  the  perpendicular  CD.  Make  the  angle 
CBE  15°,  and  draw  the  line  CE  at  right 
angles  to  BE,  then  describe  a  circle  with  C  as 
centre,  through  the  point  E.  Let  BF  be  the 
inner  pitch  of  buckets,  and  suppose  a  thread 
wound  round  the  circle  E,  and  carrying  a 
pencil  at  B  ;  as  this  is  unwound,  the  arc  BGH 
is  traced  by  the  point  B,  the  point  H  being  a 
little  to  the  left  of  the  line  JFG,  and  the  width 
of  the  passage  being,  therefore,  uniform  from 
G  to  H.  The  remainder  of  the  bucket  HA[is 
a  portion  of  a  circle,  the  tangents  AD  and 
AK  containing  the  angle  87.5°.  The  buckets 
in  the  revolving  wheel  are  constructed  similarly, 

except  that  the  angle  L  is  made  12°  instead  of  15°,  and  the  angle  M,  instead  of  87.5°, 
should  be  made  an  angle  of  90°. 

In  some  constructions  the  number  of  guide  blades  are  made  equal  to  or  nearly 
equal  to  the  number  of  wheel  blades.  In  the  vortex  we  have  only  four  or  six  guide 
blades. 

The  leading  dimensions  of  a  vortex  wheel  can  be  found  as  follows  : — 
Let  Q  =  cubic  feet  of  water  per  second,  as  before. 
h   =  the  effective  head. 
V  =  velocity  in  feet  per  second  due  to  h. 
Vi  =       »  M  ,,          in  guide  blades. 

V2=       ,,  ,,  ,,          in  inner  orifies. 


FIG.  76«. — Diagram  to  find  Curvature  of 
Turbine  Blades. 


Inward   Flow  Turbines  61 

Let  Ax  =  cross  section  guide  blade  orifice  at  discharge. 
A2=      ,,          ,,       wheel  passages. 

fj  =  radius  of  circumference  on  which  water  enters  wheel. 
rz  =         ,,  ,,  ,,  ,,      leaves  wheel. 

Now,  in  setting  out  upon  a  design  we  have  given  the  value  of  Q  and  h.  From 
this  rv  r%  can  be  calculated  if  we  fix  upon  a  limiting  number  of  revolutions  per 
minute. 

There  are  other  mechanical  calculations,  such  as  the  breadth  and  depth  of  the 
blades  and  their  number  and  their  combined  sectional  opening. 
Then  let  C2  =  the  velocity  of  inner  radius  of  wheel,  and 

C:=      ,,  ,,         outer  radius  of  wheel. 

Then  it  is  found  that  the  area  A  of  the  guide  passages  should  be  1.15  times  the 
area  A2  of  the  wheel  passages,  and  that  r^  should  be  1.17  times  r%.  And  if  there  is  a 
draught  tube,  its  area  A3  should  be  1.25  times  the  area  of  A2. 

We  can  now  proceed  with  the  design  in  figures,  starting  with  the  given  data  for 
which  a  turbine  is  required — 

Q  =  13  cubic  feet  per  second. 
h   =  36  feet  effective. 

V1  =  o.57  x8  ^  =  4.56  ^36  =  27.36  feet  per  second. 

Now,  from  construction  the  velocity  C2  at  the  inner  radius  equals  Vxx  0.966  .  •.  C2 
=  27.36  x  .996  =  26.44  feet  Per  second. 

Then,  we  can  settle  the  value  of  r^  and  r%  if  we  know  what  speed  in  revolutions 
per  second  is  required.  We  will  assume  the  speed  required  is  420  per  minute,  or  7 
per  second  ;  and  if  we  now  divide  Vl  by  speed  per  second  we  get  the  circumference 

at  7*2,  and  from  the  circumference  the  value  of  r.2  from  a  table  ;  hence  -^^  =  3-77  feet,  or 

45  inches  circumference.  From  a  table  of  circumferences  and  diameters  we  find  the 
diameter  corresponding  to  this  circumference  =  14^  inches.  Again,  to  find  rv  the  outer 
radius,  a  rule  in  practice  arrived  at  by  experience  is  r1  =  r2x  1.17,  and  as  ^  =  7.25,  r^ 
will  equal  7.25x1.17  =  8.6  inches,  or  outer  diameter=  17.2  inches.  That  rule  holds 
good  for  inward  flow  wheels  with  multiple  guide  blades, — nearly  as  many  as  wheel 
blades, — but  for  the  vortex  the  rule  is  nearer  r^  x  1.5=11  inches  nearly,  or  22  inches 
diameter.  Thus  we  have  arrived  at  the  speed  in  revolutions,  and  the  diameters  of 
the  wheel.  We  find  the  combined  area  of  the  wheel  passages  at  the  inner  radius. 

This  is  equal  to  A2  =  ^-;  hence  =      •*    =0.5   square   feet,    or   72   square   inches   clear 
V2  26.44 

opening  of  combined  wheel  passages. 

The  circumference  at  r2  is  =  45  inches.     The  number  of  blades  is  determined  by  the 

circumference  divided  by  1.5  in  inches  ;  hence  ^-  =  30  blades.    And  if  each  blade  is  |  inch 

*  o 
thick  we  get  3.75  inches  as  space  occupied  by  these  blades  by  their  thickness  on  this 

circumference  of  rz  and  the  contraction  due  to  the  angle,  as  shown  by  the  figure.  If 
we  divide  off  FB,  using  F  as  a  centre  with  radius  FG,  then  the  radius  F/  cuts  off  on 
FB  a  part  equal  to  the  opening,  and  FB  is  to  Ff  as  the  whole  circumference  is  to 
the  actual  opening ;  so  that  if  the  distance  Ff  is  o,  25  of  FB,  then  the  actual  opening  is 
as  .25  to  i,  or  45  x. 25  =  ii. 25  inches.  And  deducting  3.75  for  thickness  of  blades, 
we  get  11.25-3.75  =  7.5  inches  as  A2  on  one  side;  dividing  the  total  area  .5  square 

feet  by  7.5  we  get  -^  =  9.6  inches  as  the  axial  breadth  of  the   blades  at  the   inner 

7-5 
radius. 

The  guide  blades,  if  numerous,  must  be  calculated  in  the  same  way. 

Again,  the  ratio  between  the  radius  r^  and  r%  we  took  as  1.5  to  i,  so  that  the  breadth 
of  the  wheel  axially  may  be  reduced  outwards  in  that  ratio.  Hence,  since  the  blades 


6^ 


Modern  Engines 


are  9.6  inches  broad  at  rv  they  will  be  <-  -  at  7^  =  6.4  inches.      This  reduction  at   the 

outer  periphery  is  shown  in  Figs.  72  and  73  very  well. 

The  rest  of  the  design  is  mechanical,  such  as  the  casing,  the  bearings,  shaft,  and 
governor  ;  these  come  under  other  headings.  The  inward  flow  turbine  is  sometimes 
made  as  shown  in  Fig.  77,  an  illustration  of  a  common  form,  in  which  the  wheel  passages 
are  spiral  and  the  discharge  axial. 

Fig.  78  shows  how  this  turbine  is  conveniently  fixed  in  the  pentrough. 

Another  type  of  mixed  flow  turbine  is  well  shown  by  Messrs.  Gunther's  illustration 
of  a  large  pair  recently  made. 

We  must  consider  the  so-called  mixed  flow  turbine,  to  which  a  large  class  belong. 
Usually  they  are  inward  and  axial  flow,  and  can  be  easily  placed  in  a  timber  or  brick 
wheel  pit  with  the  draught  tube  projecting  through  the  floor. 

In  some  of  them  the  guide  blades  are  made  movable  for  regulating  purposes,  while 
some  have  a  revolving  cage  whereby  the  orifice  can  be  reduced  in  area.  The  wheel, 
usually  of  gun-metal  or  bronze,  is  shown  in  Fig.  77.  The  blades  are  curved  and 


FIG.  77. — Mixed  Flow  Turbine. 


FlG.  78. — Method  of  Fixing  Turbine. 


spiral,  leading  down  to  outward  flow  ;  curved  also  for  downward  flow  blade.  These 
types  of  turbines  are  all  difficult  to  regulate  in  speed,  but  where  close  regulation 
is  not  of  importance  they  are  cheap  to  instal,  and  give  a  good  efficiency  when  full 
loaded. 

The  mixed  flow  turbine  constructed  by  Messrs.  Gunther  has  an  axial  and  outward 
radial  flow  set  of  blades,  with  a  series  of  guide  blades  acting  much  as  the  large  blades 
in  the  vortex  wheel.  As  it  is  a  good  type  of  wheel  for  a  horizontal  shaft  and  considerable 
speeds  at  high  powers,  we  may  consider  a  good  example  of  it  recently  made  for  a  large 
mill  abroad. 

The  plant  consists  of  two  of  the  firm's  latest  type  of  mixed  flow  turbines,  in  which 
the  water  enters  on  the  outer  circumference  of  the  wheel,  and  is  discharged  partly  on 
the  inner  circumference  and  partly  in  an  axial  direction.  The  head  of  water  available 
is  35  feet,  and  each  turbine  has  been  designed  to  produce  150  horse-power  with  this 
head  at  a  speed  of  180  revolutions  per  minute.  Plate  I.  shows  the  complete  plant 
mounted  on  its  bed-plate,  consisting  of  two  cast-iron  beams,  which,  when  everything 
is  bolted  up,  form  what  is  practically  a  continuous  bed-plate.  It  will  be  seen  that  the 
two  turbines  are  placed  back  to  back  with  their  shafts  in  alignment,  and  that  there 


Mixed   Flow  Turbines 


is  a  rope  pulley  mounted  between  bearings  on  a  small  shaft  in  a  line  with  the  other  two 
shafts.  It  may  be  connected  to  either  or  both  turbines  by  means  of  two  claw  clutches 
worked  by  levers,  as  may  be  seen  in  the  illustration. 

A  question  which  readily  suggests  itself  when  looking  at  the  combined  plant  is, 
Why  were  two  turbines  used  ?  In  these  days  a  300  horse-power  turbine  is  com- 
paratively small,  and  size  would  have  been  no  obstacle  ;  moreover,  the  expense  of  a 
double  set  of  piping  would  have  been  saved.  In  this  particular  instance,  however,  it 
was  deemed  preferable  to  have  two  instead  of  one,  and  for  two  principle  reasons.  The 
first  of  these  had  reference  to  the  weight  of  any  single  portion  of  the  machinery.  Owing 
to  the  locality  for  which  the  plant  was  destined  it  was  desirable  to  keep  down  weights 
as  much  as  possible.  Then,  too,  one  turbine  can  be  used  alone  when  the  full  output  of 
300  horse-power  is  not  required. 

The  rope  pulley  is  5  feet  3  inches  in  diameter,  and  it  is  grooved  for  eighteen 
ropes,  each  i£  inch  in  diameter.  The  turbine  wheels  are  36  inches  in  diameter,  and 
the  general  construction  may  be  seen  in  Fig.  79,  which  shows  a  section  through 
the  turbine  case,  and  a  section  of  the  guide  and  wheel  vanes,  showing  the  posi- 
tion of  the  former  when  closed  and  when  fully  open.  The  casings  are  of  mild  steel 
plates  with  cast-iron  flanges  riveted  in,  and  each  turbine  is  provided  with  a  manhole 


GUIDE  BLADES 
OPEN 


Sectional  Elevation. 


Section  of  Guide  Blades  and  Wheel  Vanes. 


FlG.  79. — Large  Mixed  Flow  Turbine. 

for  examination  of  the  interior.  The  water  inlets  are  42  inches  in  diameter,  and  the 
suction  bends  36  inches  in  diameter.  The  wheel  of  either  turbine  can  be  taken  out  by 
removing  the  suction  bend  and  the  cast-iron  end  to  which  it  is  bolted,  which  does  not 
necessitate  touching  anything  on  the  pulley  side.  The  end  pressure  of  the  shaft  is  said 
to  be  very  slight,  and  to  take  it  up  a  lignum  vitae  footstep  is  provided.  This  is  placed 
in  a  small  chamber,  which  may  be  seen  bolted  to  the  outside  of  the  suction  bend.  It  is 
adjustable  for  wearing  by  means  of  the  set  screw  at  the  end  of  the  chamber,  and  it  is 
lubricated  by  the  pressure  water  taken  from  the  turbine  case  by  means  of  a  small  pipe, 
which  may  be  seen  in  the  engraving.  This  lubrication  is  so  arranged  that  the  pressure 
water  passes  up  the  centre  of  the  footstep  and  through  a  groove  across  its  diameter. 
It  is  said  that  this  construction  ensures  that  the  whole  rubbing  surface  is  efficiently 
lubricated.  As  the  pressure  water  might  contain  grit  or  sand,  measures  are  taken  to 
prevent  this  getting  into  the  bearing. 

Regulation  for  speed  or  power  is,  as  may  be  gathered  from  Fig.  79,  brought  about 
by  movement  of  the  guide  blades.  The  guide  blades  are  pivoted,  and  are  opened  or 
closed  simultaneously  by  the  rotation  of  a  ring  carrying  a  number  of  equally  placed  pins, 
one  of  each  fits  into  a  slot  in  each  guide  plate.  Quite  a  small  motion,  or  travel  of  the 
ring,  suffices  to  fully  open  or  fully  close  the  blades.  By  properly  proportioning  the 
guide  blades,  and  placing  the  pins  on  which  they  work,  matters  are  so  arranged  that 


64 


Modern   Engines 


the  blades  are  practically  in  working  balance  against  the  pressure  ot  the  water,  and 
that  consequently  the  gates  are  easily  and  quickly  opened.  As  a  result  close  governing 
is  obtained.  The  ring  which  opens  or  closes  the  guide  blades  is  worked  by  two 


FlG.  80. — Method  of  Fixing  Large  Jonval  Turbines  for  Low  Falls. 

cranks  placed   180°  apart  and  coupled  by  levers,  the  desired   motion   being  imparted 
by  the  screw  revolution  of  a  screwed  spindle. 

The  spindle  actuating  the  regulating  levers  is  provided  with  a  coupling  at  its 
upper  extremity.  This  is  taken  to  an  upper  floor  over  the  turbine  house,  and  there 
connected  to  the  regulating  pillar  and  governors. 


Pressure  Turbines  65 

PRESSURE  TURBINES 

These  are  inward  or  outward  flow  pressure  turbines  usually,  but  are  also  made  for 
axial  flow. 

This  is  the  type  ot  wheel  used  at  Niagara  Falls  in  the  large  power  scheme,  work- 
ing without  a  draught  tube,  and  they  are  outward  flow.  We  shall  refer  to  them 
again. 

But  before  the  Niagara  scheme  there  was  a  paper  mill  in  Niagara  with  a  wheel-pit 
167  feet  deep  and  28  x  43  feet  in  section,  with  a  vertical  supply  pipe  13^  feet  in  diameter, 
working  three  inverted  Jonval  turbines  of  1 100  horse-power  each.  By  inverted  is  meant 
that  the  guide  blades  were  below  and  the  wheel  above,  so  that  the  upward  water 
pressure  supported  the  weight  of  the  wheel  and  vertical  shaft,  the  shaft  being  10  inches 
diameter. 

Niagara  Falls  are  on  that  immense  chain  of  inland  lakes  on  the  boundary  between 
Canada  and  the  United  States  ;  these  lakes  are  natural  reservoirs  for  the  rainfall  over 
240,000  square  miles.  The  overflow  discharges  at  a  constant  rate  nearly,  through  the 
river  St.  Lawrence  into  the  sea.  Between  Lake  Erie  and  Lake  Ontario  the  water  flows 
through  the  river  Niagara  with  a  fall  of  326  feet  in  36  miles,  the  quantity  of  flow  is  about 
300,000  cubic  feet  per  second  ;  such  a  vast  quantity  at  such  a  high  fall  would,  if  it  could 
be  utilised,  give  up  about  7,000,000 
horse-power  night  and  day. 

In  all  these  large  powers  some 
modification  of  the  pressure  wheel  is 
used  with  a  vertical  shaft. 

The  arrangement  for  setting  large 
Jonval  turbines  in  masonry  for  low 
falls  is  shown  in  Fig.  80.  The  water 
enters  from  the  left  and  first  passes 

through  a  screen,  to  intercept  float-  'jJ^^JipaM^-^      .'. 

ing  rubbish  ;  it  then  passes  the  sluice 
valve    into    the    wheel    pit    and    falls  FIG.  81.— Jonval  Turbine  with  Horizontal  Shaft, 

through  the  wheel  into  the  tail  race. 

And  Fig.  81  shows  an  axial  turbine  of  this  class  with  a  horizontal  shaft  made  in  a 
convenient  form  for  coupling  to  a  draught  tube.  Again,  for  an  inward  flow  turbine, 
let— 

Q    =  cubic  feet  of  water  available  per  second. 

h    =  effective  head  of  water. 

V    =  velocity  of  water  due  to  fall  in  feet  per  second. 

V2  =         ,,  ,,          across  clearance  between  guide  blades  and  wheel  in 

feet  per  second. 

C    =  velocity  of  wheel  blades  at  entrance  of  water  at  rr 

C2  =         ,,  „  „  outlet  rv 

Ax  =  sectional  area  of  jet  at  discharge  of  guide  blades. 

A2  =         ,,  ,,  wheel  passages. 

A3  =         ,,  ,,  tube  or  exhaust. 

R    =  revolutions  of  shaft. 

r^    =  inner  radius  of  wheel. 

7-2    =  outer  radius  of  wheel. 

N    =  number  of  wheel  blades. 

N^=          ,,        guide  blades. 
Empirical  rules  give  the  following  data  : — 

-i=—. 
r2     1.17' 

VOL.  I. — 5 


66  Modern  Engines 

£2  =  0.25.     V2  =  o.57x8x  Jh. 

A3 

C2  =  o.96xV2.      A2=Q 

V2 

Assume  we  wish  to  calculate  a  wheel  for  100  feet  head  effectual.  Quantity  of 
water  Q  =  SO  cubic  feet  per  second  ;  speed  of  wheel,  10  per  second.  We  shall  proceed 
to  find  the  dimensions  of  the  wheel.  Thus  from  V2  =  o.57  x  8  ^  =  0.57  x  8  ^100  = 
4. 56  x  10  =  45.6  feet  per  second.  And  C2  the  velocity  of  the  wheel  at  r  its  outer  periphery 
in  an  inward  flow  turbine  =  C2  =  0.96  x  V2  =  0.96  x  45.6  =  43.7  feet  per  second. 

Q 

From  this  and  the  speed  10  revolution  per  second  we  get  r-^ ;  for  -^  will  give  us  the 

R 

circumference  in  feet,  from  which  r-^  can  easily  be  found.    Thus   ^^-^  =  4.37  feet  circum- 
ference =4.37  x  12  =  52. 44  inches,  equals  a  diameter  of  16  inches;  .'.  r->  =  —  =  8  inches,  and 

2 
g 

=  6.8  inches,  and  8  inches  for  outer  ^  in  an  inward  flow  wheel. 


1.17 

The    combined    area   of  the   guide   blade   passages  =  --  =  — — =1.15   square   feet 

V2    43-7 
=  165  square  inches  =  A1. 

From  this  and  the  number  of  blades  and  their  thickness  the  axial  depth  of  the 
wheel  can  be  calculated,  for  we  know  its  circumference  at  rr  But  besides  the  thickness 
of  the  blades  and  their  number  we  want  to  know  their  contraction  of  passages  by  their 
obliquity  to  the  radial  line  ;  this  can  be  calculated  if  we  know  the  angles.  The  angles 
will  be,  however,  better  drawn  to  instructions  given  in  Fig.  760  (p.  60)  already,  and  the 
actual  opening  F  G  measured  ;  before  drawing  it  we  must  know  the  number  of  blades. 
These  should  be  numerous  and  thin.  If  we  take  a  safe  estimate  from  practice  of  making 
them  about  1.5  inches  from  the  centre  of  one  blade  to  the  next  on  the  circumference,  this 

circumference  is  52  inches;  hence  -^  =  35  blades.      Each  blade  might  be  ^-inch  thick ; 

1'5 
hence  the  lot  will  take  up  £  x  35  about  7^  inches.     This  amount  must  be  deducted  from 

the  circumference. 

We  must  find  the  openings  on  the  diagram,  Fig.  760,  F  G,  and  suppose  we  find 
them  each  0.25  of  what  they  would  be  if  the  blades  were  truly  radial,  that  is 
to  say,  the  openings  would  be  only  J  of  what  they  would  be  with  radial  blades, 
£  of  52  =  13  inches,  and  this  -  4^,  the  thickness  of  blades  =  8£  inches  as  the  one 

side  of  the  area  of  the  outflow.    A  =  165  square  inches  ;  hence  — -5  =  20  inches,  nearly  the 

8-5 
axial  depth  of  the  wheel.      We  have  now  found — 

Diameter  of  wheel  outside  16  inches. 

,,  ,,        inside     13.6  inches. 

Area  of  guide  blade  passages  =165  square  inches,  and  the  number  and  thickness  of 
blades  from  which  we  find  the  length  axially  of  the  wheel. 
If  a  draught  tube  is  used  its  area  should  =  AX  x  1.25. 

On  this  basis  there  would  be  some  pressure,  but  very  little  where  the  water 
jumps  from  guide  blades  to  wheel  blades,  for  in  an  inward  flow  turbine  it  is  difficult 
to  get  the  r^  end  of  the  opening  larger  than  the  guide  blade  openings  ;  they  must  be 
smaller. 

In  the  axial  flow  Jonval  turbine  the  radius  t  is  the  mean  between  the  outer  and 
inner  circle  filled  by  the  wheel  passages.  Here  the  passages  Ap  A2,  A3  are  easily  found, 

A  A 

thus  Ax  =  — 2-,  and  A3  =  — 2-  ;  so  that  if  Ax=  1.15  feet,  A2  would  =  1.15  x  1.15=  1.8  square 

O  *     0 

feet.     And  A3=i.8x4  =  7.2  square  feet  opening. 


Turbine  Vanes 


PRESSURE 
10 


TURBINE  VANES 

In  the  foregoing1  calculations  values  and  constants  have  been  taken  to  show  the 
working  of  elementary  problems  in  turbines.  The  subject,  however,  can  be  treated  with 
mathematical  precision  by  geometrical,  graphic,  and  algebraic  figures  and  formulae  to 
be  found  in  classic  works.  While  the  conclusions  to  be  arrived  at  by  these  means  are 
sure  guides  as  to  the  practical  designing  and  construction,  they  cannot  be  realised 
entirely. 

In  dealing  with  guide  bladed  turbines,  in  which  the  energy  is  delivered  mostly 
by  momentum,  we  speak  of  velocities  as  "absolute"  and  "relative."  To  explain 
the  meaning  of  the  terms  we  may  refer  to  the  Pelton  jet  and  wheel  (Fig.  50).  The 
nozzle  is  fixed,  and  the  jet  issues  at  a  velocity  due  to  pressure.  This  velocity  is  absolute  ; 
it  is  the  velocity  with  which  a  particle  in  the  jet  moves  away  from  the  nozzle  to  the 
vane;  "relative"  velocity  means  the  velocity  of  something  else  compared  with  this 
absolute  velocity.  The  vane,  for  instance,  might  have  no  resistance  to  offer  to  the 
jet,  in  which  case  it  would  be  carried  forward  with  the  jet  at  the  same  velocity,  and 
the  relative  velocity  ot  the  vane  would  be  the  same  as  the  absolute  velocity.  Again, 
if  the  vane  were  fixed  there  would  be  no  relative  velocity  between  it  and  the  jet.  In  the 
first  case  the  jet  would  not  split  and  flow  back  out  of  the  vanes ;  the  vanes  would  be 
carried  along  like  a  shield  on  the  advancing  end  of  the  jet;  being  unresisted,  no  work  could 
be  got  from  it.  In  the  second  case  the  water  would 
split,  and,  if  we  neglected  friction,  would  return  with 
same  velocity,  exerting  a  pressure  only  on  the  vane. 
Now,  between  these  extreme  cases  we  have  relative 
velocities  at  which  we  obtain  motion  of  the  vane 
against  resistance,  and  there  is  a  certain  velocity 
of  the  vane  compared  with  that  of  the  jet  from 
which  we  obtain  the  greatest  amount  of  energy,  and 
that  is  a  relative  velocity  midway  between  the  two 
extremes  which  we  have  considered, — that  is,  when 
the  velocity  of  the  vane  is  half  the  velocity  of  the 
jet.  When  the  vane  had  no  resistance  against 
the  jet  its  velocity  was  equal  to  that  of  the  jet,  and  therefore  no  pressure  could  be 
obtained  upon  it.  When  the  vane  was  at  rest  full  pressure  was  obtained,  but  no 
velocity.  If  now  the  vane  is  allowed  to  move  at  half  the  jet  velocity  the  maximum 
work  done  against  the  resistance  which  controls  the  relative  velocity  for  the  pres- 
sure x  the  vane  velocity  =  the  power  obtained.  As  V  the  relative  velocity  of  the  jet 
increases,  P  the  pressure  upon  it  decreases ;  and  as  P  the  pressure  on  the  vane 
increases  (by  restraining  the  vane  to  a  lower  V),  V  decreases.  Take  a  rectangular 
parallelogram  (Fig.  82),  divide  the  top  line  to  represent  parts  of  pressure  on  the  vane, 
and  the  bottom  line  to  represent  parts  of  velocity,  numbered  from  right  to  left  for 
pressure,  and  from  left  to  right  for  velocity ;  a  perpendicular  line  anywhere  between 
the  two  ends  will  cut  the  area  into  two  parts  corresponding  to  V  and  P  respectively  in 
magnitude,  so  that  if  we  increase  the  one  area  we  decrease  the  other  in  the  same 
amount.  Suppose  we  divide  it  at  5  on  bottom  line,  then  P=i$  and  V  =  5;  hence 
P  x  V  =  75.  Divide  it  at  half,  that  is,  make  P  =  V,  then  10  x  10=  100.  Any  other  division 
than  half  will  give  a  less  result ;  hence  in  a  Pelton  wheel  the  relative  velocity  is  half 
the  absolute  velocity  for  best  effect. 

This  is  due  to  the  jet  striking  squarely  on  the  vane  in  the  direct  line  ot  motion,  and 
the  curves  deflecting  the  split  jet  to  clear  the  incoming  jet  and  effect  the  pressure.  The 
jets  leaving  the  vane  have  no  relative  velocity,  for  the  vane  is  receding  from  them  in 
the  opposite  direction  to  that  which  they  flow  in. 

But  the  case  is  different  if  the  jet  strikes  the  vane  at  an  angle  and  leaves  it  at 


to 
VELOcrrr 


FIG.  82. — Diagram  showing  Relation 
between  Pressure  and  Velocity. 


68 


Modern  Engines 


an  angle.      The  figure   representing   the  effects    is  then   a  rhomboid,   with  the  sides 

drawn  to  scale  showing  the  value  of  velocities. 

Suppose  in  Fig.  83  a  part  of  a  turbine 
wheel.  The  jet  enters  along  line  V,  its 
length  representing  its  velocity. 

We  must  resort  to  the  resolution  of 
forces  by  the  parallelogram  of  forces. 

Suppose  for  illustration  we  take  a 
_  model  to  illustrate  the  motions  of  a  body  like 
an  inclined  plane  under  a  force  acting  at  an 
angle.  It  is  not  sufficient  in  practice  merely 
to  represent  the  direction  and  magnitude  of 
forces  by  lines  and  angles  ;  it  is  better  to  see 
the  effects  first,  and  take  the  line  and  angle 
representation  afterwards.  Place  a  wedge 
with  an  angle  of  60°,  say,  at  A  on  a  plane 
movable  on  rollers  (Fig.  84),  and  have  a 

guided  sliding  rod  with  a  roller  on  the  end,  so  that  it  can  move  easily  up  or  down, 

but  not  sideways.     Now,  if  we  press  with  a  force  on  this  rod  downwards  there  will  be  a 

certain  amount  of  the  force  transmitted 

downwards,  but  owing  to  the  incline 

some  force  will  act  from  left  to  right, 

and  the  plane  will  run  forward  in  the 

direction  of  the  arrow,  while  the  rod 

will  move  downward.    And  if  the  height 

of  the  wedge  P  from  A  to  B  is  double 

the  length  CB,  as  it  is,  then  the  plane 

F  would   move   twice   as  fast  as  the    •- 

rod  W. 

Now,  if  rod  W  is  replaced  by  a          


FIG.  83. — Diagram  of  Forces  acting  on 
Turbine  Blades. 


FlG.  84. — Experiment  with  Forces  acting  on 
Inclined  Plane. 


water  jet,  CA  may  be  considered  the 

vane  of  a  turbine  ;  we  would  get  the 

same  effect,  only  the  water  would  rebound  from  the  plane. 

Referring  to  the  Fig.  83,  the  water  travels  along  line  V;  then,  if  we  draw  a  line  QB 

equal  in  length  to  a  scale  representing  the 
velocity  Vl  of  the  vanes,  then  the  relative 
velocity  of  the  jet  to  the  turbine  will  be 
=  QB.  Drawing  this  from  the  end  of 
V  parallel  with  the  turbine  motion,  and 
completing  the  parallelogram  APBQ, 
PB  will  give  the  relative  velocity  of  the 
jet.  The  absolute  velocities  when  enter- 
ing and  leaving  the  vanes  are  the  import- 
ant points,  not  the  velocity  of  flow  through 
the  vanes,  as  the  energy  given  up  de- 
pends upon  the  square  of  these  velocities, 

and  the  efficiency  would  be  — — — 


d 

FIG.  85. — Diagram  of  Forces  acting  on 
Turbine  Blades. 


The  velocity  v  must  be  reduced  to  the 
smallest  value,  and  this  depends  on  the 
velocity  Vx  of  the  vanes  and  on  the  angle  of  entrance  of  the  vanes  and  the  angles  of  exit ; 
this  also  can  be  shown  by  the  parallelogram  of  forces.  Fig.  85,  AB  represents,  again, 
the  direction  and  velocity  of  motion  of  the  jet ;  QB  represents  Vlt  the  velocity  of  the 


Turbine  Vanes 


69 


F  G 

FIG.  86. — Diagram  to  find  Curvature  of  Guide  Blades. 


turbine  blade  in  direction  and  magnitude  ;  then  join  AQ  by  a  line,  this  represents  the 
velocity  of  the  jet  relatively  to  the  turbine  =  R.  Constructing  the  parallelogram  QBed, 
with  angle  a  and  ft  equal,  we  get  Qe,  the  magnitude  and  direction  of  z>,  the  issuing 
velocity  of  the  jet  at  the  exit.  From  this  figure  it  is  easy  to  prove  that  the  smaller 
the  angles  a  and  ft  the  smaller  v  would  be,  and  that  if  the  jet  is  completely  reversed  in 
direction  v  =  ^V.  At  best  effect,  and  whatever  these  angles  may  be,  this  value  is  never 
less  than  ^  V,  but  greater  the  larger  a  is  ;  but  even  with  angles  a  and  ft  =  45°  the  lost 
effect  is  only  17  per  cent.,  and  in  practice  this  angle  varies  between  15°  and  22^°,  so 
that  the  actual  effect  of  a  variation  in  the  angles  has  not  great  influence. 

To  draw  the  vanes  of  a  parallel  flow  guide,  draw  two  lines  parallel  to  represent 
the  entering  face  and  the  exit  face 
of  the  guides  to  any  given  scale 
(Fig.  86).  Take  FG  =  the  pitch,  and 
make  the  angle  DFG  =  to  a ;  from 
G  draw  a  line  GDA  perpendicular  to 
FD. 

With  centre  A,  radius  AD,  de- 
scribe the  curve  DB  ;  proceed  with 
the  others  in  the  same  way. 

The    water    is    directed    in    the 
proper  direction  as  it  enters  and  gains  velocity  in  the  narrowing  passage  of  the  guide 
blades. 

For  the  blades  of  inward  flow  turbines  we  have  already  given  instructions  on  p.  61. 
For  outward  and  inward  flow  wheels  and  all  wheels  a  different  construction  is  required 
for  impulse  and  reaction  wheels,  as  already  described. 

Fig.  87  represents  a  method  for  setting  out  the  wheel  blade  curves.     Draw  two 

lines  representing  the  entering  and  exit  forces  of  the  wheel,  and  divide  off  the  pitch  of 

the  blades  FG.     And  as  before  for  the  guides,  raise  a  line  from  G  perpendicular  to  FE, 

having  made  the  angle  of  exit  GFE  =  B.     At  an  angle  of  45°,  from  point  E  draw  line 

B  EC    cutting  AD    at    C ;    make    the 

A  7"     —---,._ e q_    triangle    CBE    equilateral  ;     B    will 

then  be  the  centre  of  the  curve  from 
C  to  E. 

The  designing  of  turbines,  like  the 
designing  of  all  prime  movers,  is  not 
altogether  controlled  by  theoretical 
considerations.  These  are  admirable 
guides,  but  practice  and  experience 
alone  can  produce  good  designs  from 
these  theoretical  considerations. 

Turbine  makers  and  designers  keep  their  experience  among  themselves,  and  have 
their  own  methods  of  working  out  details.  The  designer  should  keep  in  view  the 
Pelton  wheel  as  an  elementary  impulse  turbine,  also  the  Hero  turbine,  as  the  elementary 
pressure  or  reaction  turbine  as  shown  in  Fig.  39,  and  also  as  shown  in  Fig.  40  drawn 
as  an  impulse  turbine. 

The  form  of  blades  shown  in  Fig.  34  of  a  Girard  wheel  is  more  of  a  curve  than 
those  seemingly  dictated  by  theory,  yet  they  are  quite  efficient. 

We  may  now  turn  to  the  question  of  governing  water  turbines.  This  is  no 
ordinary  problem.  The  chief  difficulties  arise  from  the  inertia  of  the  water,  its  weight 
and  momentum.  To  check  an  increase  of  speed  due  to  fall  of  load,  the  water  flow  must 
be  checked.  If  this  is  done  suddenly  great  pressure  results,  and  something  may  burst 
to  prevent  such  an  accident.  Air  vessels  may  be  used  on  the  mains  to  give  some 
elasticity.  Again,  if  the  water  requires  acceleration  to  increase  the  speed  when  it  falls 


F  G 

FIG.  87.— Diagram  to  find  Curvature  of  Wheel  Blades. 


Modern  Engines 


due  to  increase  of  load,  time  is  required  to  increase  its  flow.  Early  governors  were 
mostly  designed  of  great  power  and  magnitude,  in  order  to  operate  valves  or  sluices 
on  the  main  supply  ;  these,  being  large  and  subject  to  great  pressure,  were  very  sluggish 
and  useless  for  any  work  requiring  steady  driving. 

In  many  cases,  however,  the  speed  was  wonderfully  steady,  despite  the  poor 
governor  ;  this  was,  however,  due  to  the  fact  that  the  working  load,  which  could  be 
varied  to  any  extent,  was  a  small  fraction  of  the  total  load.  The  mill  gearing  is  usually 
machinery  of  a  constant  load,  being  in  most  cases  about  75  per  cent,  of  the  total,  so  that 
if  loo  horse-power  turbine  were  in  use  its  load  could  not  have  a  maximum  variation  of 
more  than  25  horse-power  out  of  100,  and  this  could  only  occur  in  the  most  unlikely 
event  of  all  the  power  on  the  variable  load  happening  to  go  off  at  once,  probably  the 
variation  in  load  on  a  turbine  working  a  mill,  through  belts,  pulleys,  spur  wheels,  and 
shafting,  never  exceed  10  per  cent,  of  the  total.  That  being  so,  the  governor  in  most 
cases  was  more  ornamental  than  useful,  and  really  acted  more  as  a  safeguard  against 
dangerous  racing  in  the  event  of  a  main  belt  or  shaft  failing. 

All  that,  however,  has  been  changed  by  electrical  transmission  of  power,  in  which 
the  variable  load  is  75  per  cent,  of  the  whole,  and  the  constant  load  correspondingly 
small,  and  it  is  quite  possible  to  throw  off  all  the  variable  load  at  once  by  the  opening 
of  a  switch  or  cut-out.  Hence  the  governor  must  be  made  to  govern  the  turbine  speed 
promptly,  and  within  a  small  variation.  The  known  governors  are  not  many,  but 
present-day  forms  of  them  are  fairly  satisfactory,  and  close  enough  governing  can  be 
obtained  by  the  best  of  them.  Some  turbines  are  easier  governed  than  others.  We 
have  referred  to  the  Pelton  wheel  governor  and  the  vortex  governor  already  in  con- 
nection with  these  wheels. 


TURBINE  GOVERNORS 

The  question  of  turbine  governing  when  constant  speed  under  varying  loads  is  one 
of  much  importance,  and  presents  some  difficulties  when  the  load  is  liable  to  sudden  and 
large  fluctuations;  especially  is  this  the  case  when  driving  electrical  generators  for 
constant  electric  pressures.  The  same  difficulty  arose  with  steam  and  gas  engines 
in  early  days,  for  until  electrical  engineering  became  a  commercial  success  the  govern- 
ing of  engines  was  not  understood.  The  marine  engine,  the  locomotive  engine,  the 
factory  engine,  traction  engine,  and  others  got  along  very  well  without  any  particularly 
good  governing.  In  most  cases  of  power  users  the  power  required  was  pretty  constant, 
for  the  gear  used  to  transmit  it  generally  took  from  40  to  70  per  cent,  of  the  maximum 
all  the  time.  The  marine  engine  cannot  run  above  its  maximum  speed  unless  the 
propeller  is  lost  or  the  propeller  shaft  broken,  or  in  storms,  when  the  propeller  may  be 
lifted  out  of  the  water.  The  locomotive  is  governed  by  the  driver  of  the  engine. 

Steam,  gas,  and  water  powers  are  governed  by  centrifugal  pendulum  governors 
as  a  rule.  This  type  of  governor,  originated  by  James  Watt,  is  capable  of  considerable 
variation  in  design. 

For  water  turbines,  wherein  the  valves  to  be  moved,  or  sluices  to  be  shut,  or  blades 
altered  in  angle,  a  hydraulic  relay  is  necessary.  The  old  attempts  to  govern  by  powerful 
governors  are  all  failures ;  mechanical  relays  also  are  failures.  A  light  sensitive 
governor  controlling  a  powerful  cylinder  and  piston  which  operates  the  valves  is  the 
only  solution  of  the  problem  at  all  satisfactory. 

The  centrifugal  governors  we  shall  treat  later  on  fully  under  "  Engine  Mechanism." 
Meanwhile,  the  points  of  interest  are  the  hydraulic  principles  used  in  the  governors  to 
operate  the  sluices  or  gates  of  the  turbine. 

In  some  old  style  turbines  a  large  pendulum  governor  was  used  to  throw  in  and  out 
two  clutches  to  gear  into  the  sluices  from  the  turbine  shaft  so  as  to  open  or  shut  them. 
But  such  governing  always  occupies  too  much  time,  and  hence  oscillations  in  speed 


Turbine  Governors 


occur  at  every  change  of  load.  If  the  load  is  increased  the  speed  decreases,  and  the 
governor  engages  the  clutch  which  opens  the  sluices  ;  but  it  takes  time  to  open  the 
sluice,  so  that  the  speed  does  not  at  once  cease  to  fall,  and  the  opening  goes  on  until 
the  speed  has  increased  somewhat  ;  it  opens  too  much,  so  that  the  speed  rises  enough  to 
throw  in  the  other  clutch  to  close  the  sluices  ;  this  closing  is  again  overdone,  and  so 
the  see-saw  in  speed  goes  on,  gradually  settling.  A  heavy 
fly-wheel  modifies  these  oscillations. 

The  relay  hydraulic  governor  shown  in  Fig.  88  was 
one  of  the  first  successful  ones.  A  piston  valve  A  with  a 
free  passage  through  the  centre  and  an  annular  passage 
acts  as  a  valve,  admitting  water  to  either  one  or  other  of 
two  piston  heads  of  different  areas.  On  the  smaller  piston 
below  there  is  a  constant  water  pressure,  tending  to  raise 
the  piston  if  the  water  above  the  large  piston  is  open  to 
discharge  through  A  and  the  overflow  ;  hence  if  the  governor 
raises  the  valve  from  the  position  shown  the  water  above 
the  large  piston  will  escape,  and  the  pressure  on  the  small 
piston  will  raise  it  until  the  valve  closes  in  the  higher  position. 

Again,  suppose 

the  valve  dropped 

from  the  position 

shown,  the   pres- 
sure     would      be 

admitted    to    the 

larger  pistonhead, 

so  that  the  piston 

would  drop  as  far 

as  the  valve   had 

dropped,    and 

would   be    locked 

in   the   new  posi- 
tion. 

The  movement 

of    the    piston 

follows,  and  tends 

to  close  the  port 

at  whatever  posi- 
tion the  governor 

shifts    the   valve  ; 

hence    the   move- 
ments of  the  small 

light     valve     are 

followed    by    the 

powerful     pistons 

as  if  the   pistons 

were  directly  con- 

nected    to    the 

governor.  The  action  is  prompt  and  positive.  The  figure  shows  this  governor  in  its 
elementary  form,  and  as  so  constituted,  is  all  that  is  required  for  sluices  requiring 
small  amounts  of  movement ;  for  long  movements  the  governor  is  connected  to  the 
valve  rod  by  a  lever,  the  fulcrum  of  which  rises  and  falls  with  the  piston. 

In  Murray's  governor  (p.  57)  the  valve  and  piston  are  separate,  so  that  a  long  stroke 
can  be  made  with  a  very  short  movement  of  the  governor  valve. 


J 

I 

r 

i  .                                       VI  I 

FIG.  88. — Relay  Hydraulic  Governor. 


FIG.  89. — Willans'  Governor. 


Modern  Engines 


Willans'  governor  can  be  actuated  by  an  electric  solenoid  operated  from  a  dynamo 
when  the  turbine  is  used  for  electrical  generating.  The  arrangement  is  shown  in 
Fig.  89,  in  which  the  governor  valve  is  inside  the  piston,  which  acts  in  the  same  way 
as  described  for  Fig.  88. 

Many  attempts  at  solenoid  governing  have  been  made,  and  Willans  contains  the 
elements  of  success  first  achieved.  Willans,  instead  of  actuating  the  throttle  valve  or 
expansion  valve  directly  by  the  electromagnet  or  solenoid,  employs  the  latter  to  actuate 
a  small  supplementary  valve,  which  is  almost  frictionless,  and  this  in  its  turn  controls 
the  supply  or  discharge  of  water,  steam,  or  other  fluid  pressure  to  a  cylinder  in  which  a 
piston  works,  which  actuates  the  throttle  valve  or  expansion  gear  of  the  engine.  In 
this  way,  although  absorbing  a  power  less  than  half  that  required  for  one  2o-candle 
lamp,  the  solenoid  is  able  to  control  the  most  powerful  expansion  gear. 

The  Willans  electric  governor  is  shown  in  Fig.  89,  where  S  is  a  solenoid  taking 
the  place,  in  incandescence  lighting,  of  one  of  the  lamps.  In  other  words,  the  solenoid 
is  on  a  branch  between  the  main  wires.  The  core  C  of  the  solenoid  is  suspended  by  a 
spring,  and  this  spring  is  attached  at  the  top  to  an  adjusting  screw  used  for  regulating 


FlG.  90. — Electric  Solenoid  Governor. 

the  light.  The  other  end  of  the  core  is  connected  with  a  small  piston  valve  working 
inside  the  main  piston  W,  which  latter  piston  controls  the  throttle  valve  in  the  casing  T. 
Water  or  other  fluid  pressure  is  admitted  by  the  pipe  P  into  an  annular  chamber 
surrounding  the  water  piston  W,  and  also,  by  means  of  a  suitable  passage  X,  into  an 
annular  space  between  the  two  small  pistons  which  form  the  piston  valve.  The  water, 
after  actuating  the  piston  W,  escapes  through  the  pipe  E,  and  by  means  of  a  small  piece 
of  flexible  pipe  not  shown. 

The  foregoing  is  a  description  from  Engineering  at  the  date  ot  the  patent.  The 
solenoid,  however,  is  not  sensitive  enough  for  small  variations  in  electric  pressure.  To 
work  either  this  relay  valve  or  Murray's  valve,  for  electric  governing,  an  electric  relay 
is  required.  And  for  this  purpose  the  author  can  recommend  a  carbon  plate  rheostatic 
relay,  in  which  the  resistance  in  a  coil  of  a  solenoid  and  plunger  is  varied  by  the  pressure 
caused  by  a  shunt  current. 

The  best  form  is  a  carbon  pile  rheostat,  such  as  that  first  employed  by  Brush  on  his 
arc  dynamos,  and  shown  in  Fig.  90.  There  are  four  columns  of  carbon  plates  in  series. 
When  the  turbine  and  dynamos  are  at  rest  the  plates  rest  loosely  on  each  other  and  on 
the  metal  blocks  B  on  the  lever  L,  so  that  the  resistance  is  high  and  little  current  passes, 
in  the  solenoid,  and  the  core  of  the  solenoid  is  at  its  lowest  point,  the  valve  being  full 


Turbine  Governors 


73 


open  for  the  water.  But  if  we  start  the  machine  it  increases  in  speed  and  the  magnet  puts 
on  pressure  on  the  carbons,  and  the  solenoid  pulls  upon  the  valve  lever  and  begins  to  close 
the  water  inlet,  so  that  a  fixed  speed  is  soon  attained  where  the  forces  balance.  The 


FIG.  91. — Centrifugal  Governor.     Sectional  Elevation. 

weights  on  the  lever  and  the  tension  on  the  spring  K  are  so  adjusted  that  this  resistance 

comes  into  play  near  the  fixed  speed.     This  device  gives  power  with  sensitiveness  ;  for 

when  properly  adjusted  the 

slight  variation  in  pressure 

on  the  carbons  causes  a  large 

difference  in  current  in  the 

regulating  solenoid. 

In  the  diagram  the  regu- 
lator solenoid  is  in  series  with 
the  carbon  resistance,  and 
the  pulling  magnet  M  in 
parallel ;  but  it  is  more  sen- 
sitive when  all  three  are  in 
series  —  the  solenoid,  the 
magnet,  and  the  resistances. 
It  is  shown  connected  to  a 
Murray  valve,  but  may  be 
used  with  other  valves,  mov- 
ing freely. 

For  controlling  the  large 
inward  flow  turbines,  gov- 
erned by  movable  guide 
blades  like  that  shown  in 
Messrs.  Gunther's  diagram 
(p.  63),  wherein  the  ring 

carrying  the  guide  blades  has  to  be  turned  through  a  few  degrees  to  open  or  close 
the  guide  passages. 

M.  Rateau,  in  his  Turbo  Machinery,  describes  the  combination  of  sensitive 
powerful  centrifugal  governor,  with  a  differential  hydraulic  ram  for  working  the 
guide  blades.  Fig.  91  is  a  longitudinal  section,  Fig.  92  a  cross  section.  The  ram  is 


FlG.  92. — Centrifugal  Governor.     Cross  Section. 


74  Modern  Engines 


jointed  to  the  long1  lever  G  on  the  controlling1  shaft  of  the  turbine.  The  cylinder  D 
is  always  connected  to  the  water  pressure,  and  C  is  put  into  connection  with  the  pressure 
or  exhaust  by  the  action  of  the  governor.  When  connected  to  the  pressure  the  ram 
moves  to  the  right,  the  ram  in  C  being  the  greater  in  area.  When  connected  to  the 
exhaust  the  ram  moves  to  the  left. 

The  valve  operated  by  the  governor  is  shown  in  Fig.  93.  It  is  fixed  to  the  inlet  of 
cylinder  D.  A  regulating  needle  AB  is  placed  to  regulate  the  exhaust  outflow.  The 
valve  is  worked  by  K  from  the  lever  H  attached  to  the  governor  under  T. 

As  the  lower  orifice  of  the  cylinder  D  is  connected  to  the  water  under  pressure, 
while  the  upper  orifice  is  in  connection  with  the  exhaust  to  the  atmosphere,  and  the 
space  between  these  two  orifices  is  in  communication  with  the  large  cylinder  C,  we 
see  that  when  the  index  of  the  governor  rises  and  the  valve  S  is  lowered  the  upper 
orifice  is  closed  and  the  water  under  pressure  flows  into  the  cylinder  C  by  the  lower 
orifice  ;  and  when,  on  the  other  hand,  the  index  descends,  the  valve  S  rises  and  opens 
fully  the  upper  orifice,  which  has  a  section  almost  double  that  of  the  lower,  so  that  the 
pressure  falls  in  C  and  the  water  escapes  from  it.  If,  now,  the  valve  is  midway  between 
these  two  positions,  so  that  the  two  orifices  present  the  same  section  to  the  water,  the 
pressure  in  the  cylinder  C  remains  about  midway  between  the  initial  pressure  of 
the  water,  and  the  pressures  on  the  differential  piston  AB  are  balanced  so  that  it  does 
not  move.  There  is,  however,  this  disadvantage,  that  there  is  an  almost  continual  flow 
of  water  through  m.  On  the  other  hand,  there  are  two  great  advantages :  first,  the 
small  valve  S  is  only  rarely  forced  to  the  end  of  its  stroke  by  the  governor  ;  generally  it 
is  only  partially  moved,  and  from  this  results  a  speed  of  gate  opening  or  closing  more 
or  less  great.  The  point  of  rotation  d  of  the  lever  H  is  not  really  fixed  ;  it  is  connected 
to  the  piston  valve  in  such  a  manner  that  it  rises  or  falls  proportionally  to  the  motion  of 
this  piston.  It  results  from  this,  that  when  the  piston  is  at  rest,  and  consequently  the 
valve  S  occupies  its  mean  position  as  well  as  the  point  e,  the  index  i  of  the  governor  is 
obliged  to  fix  itself  in  the  position  corresponding  to  that  of  the  point  d,  and,  reciprocally, 
the  point  d  and  the  piston  valve  are  obliged  to  follow  the  movement  of  the  index. 

This  device  of  making  the  fulcrum  rise  and  fall  with  the  movement  of  the  governor 
is  an  old  one,  and  was  used  in  the  Willans'  governor  in  1884,  and  we  have  already 
explained  that  it  is  used  on  the  governor  in  Fig.  88  (p.  71). 

On  the  whole  question  of  water  turbine  governors  it  may  be  taken  that  all  the  best 
makers  have  adopted  effective  hydraulic  relay  governing,  and  that  close  governing  is 
obtained  under  all  loads  ;  but  the  load  should  not  be  varied  suddenly  to  any  large 
extent, — not  because  the  governor  would  not  act,  but  to  avoid  the  effects  of  the  inertia 
of  the  flowing  water  in  the  pipes  and  valves. 

In  order  to  prevent  the  bursting  of  the  pipes  when  the  flow  is  suddenly  checked  by 
the  governor,  ample  relief  valves  are  often  provided.  These  are  shown  distinctly  in 
Messrs.  Gunther's  illustrations. 

Some  turbines,  notably  the  inward  flow  types,  are  more  stable  than  others,  due  to 
the  flow  being  opposite  in  direction  to  the  centrifugal  force  on  the  whirling  water. 

In  cases  where  water  is  not  abundant  and  sometimes  small  in  quantity  it  is  better 
to  use  several  turbines,  and  to  run  the  number  sufficient  to  use  the  available  water  at 
any  time,  than  to  use  one  large  turbine  and  work  it  at  ^,  |,  or  f ,  or  whole  gate  ;  but 
where  economy  of  water  is  no  object  the  large  turbine  is  cheaper  in  first  cost  and 
maintenance. 

Other  makers  of  governors  exist,  but  it  is  difficult  to  get  exact  information  of 
their  design  ;  but  all  of  them  working  with  centrifugal  governors  are  on  the  relay 
principles,  as  described  herein. 

Gunther's  turbines  are  operated  by  separate  governor  valve  and  piston,  same  as 
Murray's  governor.  This  arrangement  is  shown  in  Messrs.  Gunther's  improved  Pelton 
wheel  turbine  or  high  pressure  impulse  wheel,  shown  in  Fig.  94. 


Turbine  Governors 


75 


That  their  governor  is  a  high-class  one  may  be  seen  from  the  following'  test  results 
at  an  installation  with  a  Gunther  turbine  and  governor  : — 

Turbine  at  Landore  Hotel,  Keswick. — This  is  a  Girard  turbine  fitted  with  a  Gunther 
governor  as  described.  Fall,  300  feet ;  horse-power,  15;  wheel,  15"  internal  diameter; 
speed,  850  revolutions  ;  coupled  direct  to  multipolar  dynamo  of  75  amperes  at  130  volts. 
Used  for  lighting  the  hotel  and  charging  an  electric  launch  running  on  Derwentwater 
Lake. 

The  lights  are  driven  direct  without  cells,  and  the  cables  run  down  to  the  pier  and 
charge  direct  into  the  cells  on  board  the  launch  as  required.  The  following  are  the 
results  of  actual  trials  with  the  governor: — No  perceptible  variation  of  speed  was 
noticeable  on  the  tachometer  with  sudden  load  changes  of  10  per  cent.  ;  with  a  sudden 
throwing  off  of  one-third  the  total  load  by  throwing  out  a  switch,  the  speed  rose 
temporarily  only  about  20  revolutions  in  850  revolutions,  equal  to  z\  per  cent.,  and  then 
came  back  to  normal.  The  turbine  is  usually  left  running  with  the  governor  all  through 
the  night,  the  turbine  house  being  locked  up  at  11.30  p.m.,  and 
the  attendant  coming  back  at  about  7.30  a.m. 

This  plant  is  shown  from  a  photo  in  Plate  II.,  wherein  the 
governor  exterior  can  be  seen. 

Much  larger  turbines  of  the  same  design  are  shown.  In 
Plate  III.  is  shown  a  view  of  high  pressure  type  of  impulse 
turbine  with  single  jet,  the  illustration  being  from  a  photo  of 
one  of  a  set  of  turbines  recently  made  for  the  Indian  Govern- 
ment for  utilising  the  Karteri  Falls  in  the  Nilghiri  Hills,  the 
power  being  transmitted  electrically  to  the  Coonoor  Cordite 
Factory. 

The  plant  comprises  four  of  these  turbines,  each  capable 
of  driving  250  B.H.P.  with  a  fall  of  620  feet,  and  two  similar 
but  smaller  turbines  of  37  B.H.P.  each,  for  driving  the  exciter 
dynamos.  The  large  turbines  are  coupled  direct  to  three  phase 
generators  of  5500  volts,  and  the  smaller  ones  are  also  coupled 
direct,  flexible  couplings  being  used  to  couple  the  turbines  and 
dynamos  in  each  instance  ;  and  fly-wheels  are  also  placed  on 
the  turbine  shafts  to  obtain  the  utmost  steadiness  under  load 
changes. 

In  Fig.  94  we  give  a  diagrammatic  outline  of  the  tur- 
bine, showing  the  port  and  wheel  vanes  in  section.  It  will 
be  seen  that  the  water  enters  on  the  outer  circumference  of 


FIG.  93. — Valve  of  Centri- 
fugal Governor. 


the  wheel,  and  that  the  discharge  is  towards  the  centre,  but  in  reality  the  greater  part 
of  the  discharge  is  at  the  sides.  As  in  the  other  view,  the  buckets  or  vanes  are 
cupshaped,  so  that  the  water  discharges  partly  towards  the  centre  and  partly  at  the 
sides.  The  wheel  vanes  are  cast  in  bronze  in  a  continuous  ring,  which  is  bolted 
to  a  central  cast-iron  plate.  The  guide  port  is  provided  with  a  sliding  hood  or 
shed,  by  which  the  area  of  the  discharge  is  varied  according  to  the  power  required. 
The  lower  part  of  the  shield  where  it  cuts  off  the  water  being  properly  formed  so 
as  to  make  it  a  prolongation  of  the  guide  pert  and  preserve  the  true  shape  of  the 
issuing  jet,  so  that  the  efficiency  is  practically  the  same  whether  the  port  is  full  or  only 
part  open. 

The  four  large  wheels  are  54  inches  diameter  and  make  400  revolutions  per  minute, 
and  the  two  small  ones  27  inches  diameter  and  make  800  revolutions  per  minute. 

Each  turbine  is  provided  with  Messrs.  W.  Gunther  &  Sons'  hydraulic  governors, 
and  also  with  relief  valve  to  minimise  the  danger  from  concussion  in  the  pipes  when  load 
is  suddenly  thrown  off  and  the  supply  of  water  checked  by  the  closing  or  partial  closing 
of  the  regulating  hood.  In  this  hydraulic  governor  the  rise  and  fall  of  the  governor 


Modern  Engines 


balls  opens  or  closes  a  small  valve  which  admits  pressure  water  taken  from  the  pipe 
main  to  one  side  or  other  of  a  hydraulic  cylinder,  and  thus  moves  the  piston  up  or  down, 


FIG.  94. — High  Pressure  Impulse  Wheel  and  Governor. 

and  the  motion  of  the  piston  is  communicated  by  suitable  lever  or  other  connections  to 
the  regulating-  hood,  closing1  or  opening  the  jet  as  load  is  thrown  off  or  on.     The  action 

of  this  governor  is  instantaneous,  and  brings  the 
speed  back  to  normal  at  all  loads,  that  is,  the 
speed  of  the  turbine  is  kept  the  same  at  all  loads 
between  no'  load  and  full  load. 

Referring  to  the  diagram  Fig.  94,  A  is  the  pres- 
sure pipe,  which  takes  the  water  from  the  main 
from  a  branch  on  the  turbine  inlet,  a  filter  being 
affixed  to  the  branch  so  that  the  water  is  filtered 
to  remove  injurious  particles  before  it  passes  to 
the  governor.  The  pipe  A  (shown  as  a  dotted 
line)  conducts  the  water  through  a  special  valve 
(which  is  used  also  for  stopping  and  starting  the 
turbine  hydraulically  by  means  of  the  handle  B). 
From  this  valve  the  water  passes  through  a  piston 
valve  contained  in  the  valve  box  C,  which  piston 
valve  is  worked  from  the  governor  balls,  and  dis- 
tributes the  water  to  one  or  the  other  end  of  the 
cylinder  F  through  the  pipes  D  or  E.  By  means 
of  the  valve  at  B  the  turbine  can  be  started  and 
stopped  ;  or  if  desired,  the  governor  can  be  thrown 
out  of  action  and  the  turbine  kept  running  at  any 
desired  fixed  gate  opening. 

In  considering  water  wheel  governors  we  have 


FIG.  95  —Watson,  Laidlaw,  &  Co.'s  Governor. 


described  the  American  forms  of  Pelton  wheel  gov- 
ernors. Recently  a  much  improved  automatic  governor,  by  Messrs.  Watson,  Laidlaw, 
&  Co.,  Glasgow,  has  been  brought  out,  and  is  described  in  Engineering  as  follows: — 


Turbine  Governors 


77 


The  wheel  casing"  with  the  governor  in  position  is  shown  in  Fig.  95,  whilst  Fig.  96 
represents  a  section  through  the  jet  nozzle. 

The  rod  on  core  A  is  extended  behind,  and  enlarged  in  diameter,  to  form  the  plunger 
B,  which  fits  closely  into  a  liner  within  the  body  of  the  nozzle.  The  helical  spring  inside 
the  plunger  exerts  a  constant  pressure  upon  it,  and  tends  to  thrust  the  rod  forward 
into  the  water  jet,  while  at  the  same  time  the  pressure  of  the  water  which  enters  at  D 
tends  to  push  the  plunger  back  with  greater  force.  The  small  holes  E  in  the  end  of  the 
plunger  permit  a  certain  quantity  of  water  to  pass  into  the  chamber  behind  the  plunger  ; 
and  if  the  valve  F,  which  communicates  with  the  exhaust  chamber  G,  be  closed,  the 
pressure  behind  the  plunger  will  rise  until  it  equals  that  in  front,  leaving  the  spring  free 
to  act  without  opposition.  It  is  therefore  apparent  that  the  full  closing  of  the  valve  F 
has  the  effect  of  reducing  the  water  gate  to  its  minimum 
by  allowing-  the  spring  to  act  freely  ;  while  the  contrary 
effect  will  result  from  the  full  opening  of  the  valve,  owing 
to  the  effect  of  the  water  pressure  on  the  plunger  being 
greater  than  the  power  of  the  spring. 

Partial   opening   of  the   valve  F  will   produce  water 
gates  intermediate  between  the  maximum  and  minimum, 
owing  to  the  tapered  form  of  the   rod  or  core  A.      Full 
control  of  the  wheel  is  therefore  effected  by  the  closing 
and  opening  of  the  valve  F  being-  made  dependent  upon   FlG- 
the  higher  or  lower  speed  at  which  the  wheel  runs.     This 
result  is  attained  through  the  operation  of  the  governor 
shown    on    Fig-.    97.      The    weights    or    pendulums    H 
are  attached    elastically  to 
the  disc  J,  which  is  fixed  to 
the  wheel  spindle   and  re- 
volves with  it.      They  are 
held  together  by  springs  of 
suitable  strength,  to   keep 
them  in  position  till  a  speed 
above     normal     has     been 
reached.      Thereupon  they 
fly  out,  engaging  on  their 
leather  -  covered      surfaces 
with  the  inner  rim  of  the 
loose  pulley  K,  which  they 
tend    to    pull    round    with 
them.       The   boss   of  this 
pulley  has,  however,  a  chain 


tion  of  Jet 
Nozzle  of 
Watson, 
Laidlaw,  & 
Co.'s  Gov- 
ernor. 


Elevation. 


Cross  Section. 


FlG.  97. — Watson,  Laidlaw,  &  Co.'s  Governor. 


wound  round  it,  attached  to  the  spring,  and  the  friction  of  the  pendulums  H  has  to  over- 
come the  tension  of  this  spring  before  they  can  cause  the  loose  pulley  to  turn.  The  loose 
pulley  is  prevented  from  revolving  through  more  than  one  revolution  by  the  pin  L  ;  but 
at  all  speeds  materially  over  normal  the  action  of  the  pendulum  will  tend  to  draw  the 
pulley  over  through  an  arc  of  a  circle  corresponding  to  the  exact  amount  of  the  excess 
speed.  It  only  remains  to  communicate  this  action  to  the  spindle  of  the  valve  F  in  order 
to  make  the  size  of  the  water  jet  dependent  upon  the  speed  of  the  wheel.  This  is  done 
by  leading  the  chain  over  a  wheel  on  the  spindle  of  the  valve,  as  shown  in  Fig.  95. 

The  governor  is  very  sensitive,  and  can  be  adjusted  to  control  the  speed  of  the  wheel 
within  any  required  degree  of  variation  of  speed  under  great  and  sudden  changes  of 
load.  It  will  be  seen  that  this  governor  can  be  made  to  govern  in  two  distinct  ways. 
It  can  be  so  set  as  to  govern  the  jet  by  regulating  the  flow  of  water  proportionally  to  the 
load,  or  it  can  govern  by  opening  the  jet  full  and  closing  it  quite  shut,  so  that  the  time 


78  Modern   Engines 

during"  which  water  plays  on  the  wheel  is  proportionate  to  the  load.  In  either  case  the 
total  amount  of  water  discharged  from  the  nozzle  is  proportionate  to  the  work  done. 

As  the  Pelton  wheel  is  specially  suitable  for  high  speeds  and  falls  and  in  electrical 
engineering-,  an  automatic,  sensitive,  and  efficient  governor  is  of  utmost  importance  ;  but 
the  difficulties  which  might  arise  from  the  hydraulic  ram  effect  of  opening  and  closing  the 
jet  entirely  and  quickly  have  not  been  referred  to,  although  some  means  of  meeting-  will 
be  required. 

Turbine  construction  in  Great  Britain  is  fairly  well  represented  by  these  examples, 
and  in  recent  years  it  has  received  a  very  considerable  impulse  from  the  perfection  of 
electric  transmission  of  power,  enabling  the  power  to  be  carried  to  the  works  at  a  more 
suitable  place  than  where  the  waterfall  exists. 

It  is  to  the  engineer  not  much  short  of  a  public  wrong  that  the  greed  of  landowners 
should  prohibit  in  many  cases  the  use  of  large  powers  given  freely  and  gratis  by  Nature 
in  the  shape  of  waterfalls. 

A  source  of  power  running  to  waste  is  nowadays  a  wilful  waste,  and  many  such 
exist  where  the  power  could  be  obtained  and  utilised  at  a  distance  without  in  any  way 
damaging  the  land  or  the  amenities  of  the  neighbourhood. 

The  case  was  different  when  the  mill  or  factory  had  to  be  built  adjoining  the  fall ; 
whereas  now  a  distance  up  to  5  miles  is  not  an  obstacle  to  the  use  of  the  power. 

And  again,  in  hilly  countries — Ireland,  Scotland,  North-West  England,  and  parts  of 
Wales — waterfalls  can  be  produced  by  the  engineer,  in  many  cases  at  a  cost  well  worth 
the  outlay,  if  the  land  could  be  obtained  at  its  true  value.  In  most  instances,  however, 
any  such  proposals  have  the  instant  effect  of  converting  the  land  from  a  worthless  moor 
or  bog  into  most  valuable  property  at  a  value  prohibitive.  A  high  fall  with  plenty  of 
water  is  a  valuable  gift  of  Nature  to  the  landowner,  and  so  is  the  side  of  a  hill  where  an 
engineer  can  form  a  reservoir  and  catch  water.  But  as  things  are,  they  are  of  little  use 
or  value  to  the  human  race  or  the  inhabitants  of  the  country. 

FLUID-ON-FLUID  PRESSURE  ENGINES 

These  might  be  classed  among  pumps,  as  they  are  usually  employed  for  lifting 
water,  but  we  wish  to  keep  the  hydraulic  and  pneumatic  machinery  in  one  book. 

Many  machines  are  retained  in  use  by  engineers  although  they  are  well  known  to  be 
inefficient ;  this  is  only  tolerable  on  account  of  great  simplicity,  reliability,  or  portability, 
rendering  them  preferable  under  the  circumstances  to  a  more  efficiently  complex  or 
cumbrous  machine.  A  piston  pump  properly  designed  is  highly  efficient,  but  it  has 
many  delicate  parts — packing-  glands,  shafts,  fly-wheel,  cranks,  and  rods — all  accurately 
fitted  and  requiring-  care  and  attention,  and  only  possible  of  construction  in  a  well- 
equipped  machine  shop.  Water  may  be  moved  up  to  a  higher  level  from  a  well  or  mine 
by  a  waterfall,  or  by  steam,  by  very  simple  but  inefficient  means.  Thus  in  Hungarian 
mines  long  ago  water  was  pumped  out  of  them  to  keep  them  dry  by  means  of  a  fall  of 
water  working-  a  simple  arrangement  of  pipes  and  vessels,  such  as  could  be  readily 
obtained  and  set  up  by  a  country  blacksmith. 

The  Hungarian  machine  was  described  by  Professor  Rankine,  who  investigated  it 
fully  mathematically.  It  is  based  on  the  principle  propounded  by  Hero  of  steam  turbine 
fame  in  the  second  century  B.C.,  and  is  the  progenitor  of  many  modern  engineering 
apparatus.  From  Hero's  description  the  apparatus  was  somewhat  like  the  diagram  Fig. 
98,  from  which  a  working  model  may  be  made  with  two  Wolffs  bottles,  three  tubes,  and 
a  funnel,  and  five  or  six  rubber  corks.  To  show  the  experiment,  bottle  B  is  filled  with 
water,  the  discharge  pipe  D  goes  to  the  bottom  of  this  bottle  ;  F,  the  air  pipe,  just  enters 
bottles  A  and  B  ;  K,  the  supply  pipe,  goes  to  the  bottom  of  A.  To  start  the  action,  a  little 
water  is  filled  into  the  funnel,  this  water  entering  vessel  A  displaces  the  air  through 
pipe  F  into  vessel  B,  and  thus  presses  upon  the  water  in  B  and  forces  it  up  the  delivery 


Hungarian  Machine 


79 


pipe  D,  which  pipe  may  be  inclined  so  that  the  water  falls  into  the  funnel  and  maintains 
the  action  until  all  the  water  is  discharged  from  B.  In  this  experiment  the  water  is 
raised  from  vessel  B  to  a  higher  level. 

Vessels  A  and  B  may  be  placed  on  different  levels  ;  they  may  be  on  the  same  level, 
by  shortening  pipe  F  and  keeping  pipe  K  long,  as  it  is. 

In  the  Hungarian  machine  (Fig.  98),  vessel  A  is  at  the  head  of  the  pit  to  be  drained, 
B  is  at  the  bottom.  In  this  experiment  the  cork  V  is  withdrawn,  and  B  being  in  a  tub  of 
water,  it  fills  with  watef  ;  now  shut  V  and  allow  water  to  fall  into  the  funnel  through  K. 
Vx  being  shut,  air  will  be  forced  through  F 
into  B,  and  this  air  will  force  the  water  up 
from  B  through  D  to  the  pit  head.  When 
bottle  B  is  empty  bottle  A  will  be  full ;  the 
water  is  then  shut  off  and  V  and  Vx  opened, 
when  B  will  fill  again  and  A  empty,  drawing 


Hero's  Experiment.  Experimental  Hungarian  Machine. 

FIG.  98. — Hungarian  Machines. 

in  air.     V  and  Vl  are  then  shut,  the  water  turned  on  again,  and  another  bottle  full  of 
water  pumped  up,  and  so  on  until  the  level  of  the  water  is  reduced. 

Professor  Rankine's  description  is  as  follows,  referring  to  Fig.  99 : — 
A  is  the  sumpt  at  the  bottom  of  the  mine  into  which  the  water  collects.     B  is  a 
receiver  with  a  non-return  valve  C.     D  is  the  delivery  pipe  from  the  bottom  of  the  re- 
ceiver ;  there  should  be  a  foot  valve.     G,  the  waste  air  cock,  at  the  top  of  E.     The  dis- 
charge valve  at  the  bottom  of  E  is  for  discharging  the  water  which  has  performed  its 
work  in  the  working  barrel.     K,  the  supply  pipe,  connecting  reservoir  with  the  bottom  of 
the  working  barrel  E.     There  is  an  admission  valve  near  the  bottom  of  the  supply  pipe. 
The  valve  may  be  opened  and  shut  by  floats  in  the  working  barrel,  or  by  a  small 


8o 


Modern  Engines 


auxiliary  water  pressure  engine,  or  by  a  small  wheel  driven  by  the  water  discharged. 
A  single  piston  valve  is  best,  as  shown  in  Figure. 

The  machine  is  set  to  work  by  opening  the  air  waste  cock  G,  the  supply  valve  at  the 
same  time  being  shut.  The  water  from  the  well  A  opens  the  clack  C,  enters  and  fills  the 
working  barrel  B,  and  drives  out  the  air  through  G,  so  that  E  and  F  only  remain  filled 
with  air.  Then  G  is  shut,  and  remains  shut  while  the  machine  is  working  ;  the  discharge 
valve  is  shut  and  the  supply  from  K  to  E  opened,  and  the  working  proceeds  as  follows  : — 
The  driving  water  descends  through  K  into  E,  and  compresses  the  air  contained  in  E 

and  F.  The  pressure  so  exerted 
on  that  air  is  transmitted  to 
the  water  in  B,  and  causes  it 
to  rise  in  the  delivery  pipe  D. 
When  the  pressure  has  become 
equal  to  that  of  the  column  of 
water  in  D  added  to  its  resist- 
ance, the  lifted  water  issues 
from  D  into  the  drain,  and 
continues  to  do  so  until  E  is 
filled  with  water.  Then  by  the 
valve  gearing  the  supply  valve 
is  shut  and  the  discharge 
opened  ;  and  the  water  in  E  is 
made  to  flow  out,  partly  by  its 
own  weight  and  partly  by  the 
pressure  of  the  expanding  air. 
As  soon  as  the  air  has  fallen  to 
its  original  pressure  more  water 
from  the  well  flows  through  C 
into  B,  and  drives  all  the  air 
back  into  F  and  E.  Then  the 
discharge  valve  is  shut  and  the 
supply  opened,  and  the  cycle  of 
operations  recommences. 

Let  hQ  denote  the  head  of 
water  which  is  equivalent  to  i 
atmosphere,  or  33.9  feet  on  an 
average. 

Let  h^  be  the  height  of  the 
outlet  of  the  delivery  pipe  D 
above  the  surface  of  the  water 
in  A ;  D,  the  weight  of  a 
cubic  foot  of  water,  or  62.4 
Ibs. ;  Qp  the  number  of  cubic  feet  per  second  to  be  raised ;  then  DQ^  is  the  useful 
work  per  second. 

Let  h^  be  the  head  lost  by  the  resistance  in  the  pipe  D,  hQ  +  h^  +  h^  is  the  head  of 
water  equivalent  to  the  pressure  to  which  the  air  must  be  compressed  in  E,  F,  and  B 

before  the  water  will  issue  from  the  outlet  of  D.     That  pressure,  in  atmospheres,  may  be 

&    i  i, 
expressed  thus  :    n  =  i  +  -i— — -,   and  the  working  pressure  which  the  barrels  and  air 

pipe  must  be  adapted  to  bear  is  n—  i  atmospheres. 

The  volume  of  air  which  must  pass  per  second  from  E  into  B,  while  the  water  is 
being  forced  out  of  B,  is  Qx  cubic  feet  at  the  pressure  of  n  atmospheres. 

Therefore,  as  the  original  pressure  of  the  air,   before  being  compressed  by  the 


FIG.  99. — Hungarian  Machine. 


Pulsometer 


81 


descent  of  the  water  into  E,  is  i  atmosphere,  the  volume  of  the  mass  of  air  which 
descends  per  second,  at  the  original  pressure,  is  Q  =  nQl ;  and  this  also  is  the  volume  of 
water  which  must  descend  from  the  source  per  second  in  order  to  perform  the  work. 

Let  B  and  E  be  taken  respectively  to  represent  the  capacities  of  those  portions  of 
the  pump  barrel  and  working-  barrel  which  are  alternately  filled  and  emptied  of  water 
at  each  stroke,  and  let  F  denote  the  capacity  of  the 


ar   pipe 
Let   h. 


F  4-  F 

then   we   must   evidently  have  — — —  =  n. 

B  +  F 

3  be  the  loss  of  head  by  the  resistance  of 
the  supply  pipe,  valves,  etc.  Then  the  total  head 
required  for  the  fall  is  H  =  k1  +  h2  +  h3,  so  that 
the  total  energy  expended  per  second  is  DQH  = 


Comparing    this    with    DQA,    the    efficiency    is 
found — 


Q  H 


factor  -  in 


Valves  of  Pulsometer. 


The  reduction  ot  efficiency  by   the 

the  above,   corresponding  to  loss  of  head  equal   to 
(i--]H,  is  the  loss  of  energy  due  to  compressing 

the  air  and  water  friction. 

We  have  already  referred  to  the  Thomson  jet 
pump  (p.  40).  We  may  now  refer  to  the  pulsometer 
pump,  which  is  also  a  fluid-on-fluid  pump  ;  steam 
being  directly  applied  to  the  water  to  force  it  out, 
a  vacuum  is  formed  by  the  condensation  of  the  steam, 
which  by  suction  draws  the  water  up  into  the  pump. 
In  this  place  we  will  only  refer  to  it  briefly  to  show 
its  principles  of  action  ;  its  construction  falls  under 
the  head  of  Pumps. 

Referring  to  Fig.  100,  there  are  two  side  chambers 
AA  to  receive  the  water  alternately,  and  an  inter- 
mediate vessel  H,  whose  purpose  will  be  explained. 
EE  are  suction  and  GG  delivery  valves  (Fig.  100),  B  a 
foot  valve,  N  the  delivery  chamber  connected  to  A  by 
short  pipes  FF,  and  Q  the  rising  main  or  delivery 
pipe.  To  start  the  pump,  the  three  vessels  are  filled 
through  the  hole  C,  the  water  resting  on  foot  valve 
B.  The  ball  L  being  compelled  to  lie  on  one  or  the 
other  seat  JJ,  steam  is  admitted  at  K,  and,  entering, 
say,  the  right-hand  passage,  displaces  the  water 
through  F,  until  the  level  falls  to  the  upper  edge  of 
the  orifice.  Steam  then  blows  through  into  F  with  some  violence,  causing  a  partial 
vacuum  in  A.  The  ball  being  now  drawn  to  the  right-hand  seat,  water  rises  into  the 
right  chamber  ready  for  the  next  stroke,  steam  enters  the  left  chamber,  and  the  action 
is  continuously  repeated.  The  vessel  H  serves  the  purpose  of  an  air  vessel,  to  steady 
the  flow  into  N  ;  and  to  prevent  the  sudden  shock  caused  by  the  rush  of  suction  water, 
air  cocks  DD  are  placed  on  the  three  vessels,  and  kept  open.  The  "Grel"  valve 
(Fig.  101)  at  P  is  applied  to  economise  the  steam  supply.  It  is  a  short  hollow  piston, 
VOL  i.  —  6 


FIG.  100. — Pulsometer. 


82 


Modern  Engines 


which  rises  and  falls  on  account  of  the  difference  of  pressure  within  and  without  it, 
thus  closing-  the  pipe  K  after  a  portion  of  the  stroke  has  been  completed ;  the 
remainder  of  the  stroke  being  com- 
pleted by  steam  expansion. 

It  is  not  economical  by  any  means, 
but  it  is  nevertheless  a  very  useful 
and,  in  many  cases,  indispensable 
machine. 

w 

The   hydraulic   ram    next  claims 


FIG.  ioi. — Grell  Valve. 


FIG.  102. — Hydraulic  Ram. 


our  attention.      Here  we  have  a  machine  or  engine  not  only  simple,  but  highly  efficient, 
and  a  valuable  means  for  providing  a  high  pressure  water  supply  from  a  low  fall  of  water. 

Hydraulic  rams  are  divided  into  two 
classes.  In  the  first,  the  water  of  the 
fall  is  employed  to  raise  a  portion  of  itself 
to  a  higher  level ;  in  the  second,  the  fall 
is  used  to  raise  some  other  water  or  fluid 
to  a  higher  level,  and  hence  they  are  called 
pumping1  rams. 

The  principles  of  action  are  simple. 
If  water  is  allowed  to  flow  freely  through 
a  long  pipe  it  acquires  a  certain  velocity, 
due  to  the  difference  in  height  between 
the  upper  and  lower  end,  and  if  the  lower 
end  is  suddenly  closed  the  whole  column 
of  moving  water  in  the  pipe,  in  stopping, 
delivers  up  its  momentum  by  pressing 
violently  against  the  stop  and  the  sides 
of  the  pipe  ;  and  if  we  had  a  small  valve 
on  the  side  of  the  pipe  near  the  stop,  the 
water  would  be  forced  out  with  consider- 
able pressure  in  a  sudden  spurt. 

It  is  thus  only  necessary  to  have  a  long 
pipe,  with  one  end  in  the  water  supply 
and  the  other  end  some  feet  below  the 
water  level,  with  a  stopper  valve  and  a 
delivery  valve  ;  an  air  vessel  is  added  in 
order  to  regulate  the  pressure.  The 
stopper  valve  is  called  the  pulse  valve, 
because  it  beats  regularly  when  the 
pump  is  in  action.  The  construction  may  be  gathered  from  Fig.  102. 

Into  socket  A  the  supply  pipe  fits  ;  this  pipe  is  called  the  drive  pipe.     B  is  the  pulse 


FIG.  103. — Balanced  Pulse  Valve. 


Hydraulic  Rams 


valve  and  D  the  delivery  valve  ;   C  is  the  air  vessel  and  E  the  rising  main.     It  will  be 

obvious  that  a  great  deal  depends  upon  the  weights  and  sizes  of  the  valves,  especially 

of  the  pulse  valve  B.     If  it  is  too  heavy  it  will  not  close  when  the  water  acquires  its 

full   velocity  in   flowing  out  of  it  ;    if  it   is   too   light,  then   it   will   close  before   the 

water   has   acquired  the  full  velocity 

due    to    the    fall.       Hydraulic    rams 

made  on  this  simple  plan  are  there- 
fore  not   easily  adapted  to   different 

falls :    the    pulse    valve    suitable    for 

one  fall  not  being  correct  for  another 

fall. 

Again,  in   order   to   get  the  full 

force  of  the  fall  the  pulse  valve  must 

have  a  large   opening   to   allow   the 

water   free   exit,  so  that  it  becomes 

heavy.     It  is  therefore  clear  that  this 

valve     should    be    balanced     by    an 

adjustable  spring  or  weight,  so  that 

it  can  readily  be   adjusted  to  obtain 

the  best  effects  under  all   conditions 

of  working.     This  improvement  was 

made  by  Mr.  Keith,  whose  machine  is 

shown  in  Fig.  103.      The  valve  B  is 

hung  on  a  lever  N  and  balanced  by 

a  weight  J,  so  that  it  can  be  nicely 

adjusted    to   open   and   close   at   the 

right  time  on  any  fall. 

Another  balanced  ram  is  shown 

in  Fig.  104,  an  American  design.    The  FIG.  104. — Balanced  Pulse  Valve. 

pulse  valve  is  a  piston  form  guided  at 

the  lower  end  in  a  socket,  which  has  a  rubber  stop  to  silence  the  beats  ;  it  is  balanced 

by  weight  G  on  lever  F. 

In  this  ram  there  is  a  device  for  maintaining  air  in  the  air  vessel.     Air  is  absorbed 

by  water  under  pressure,  and  hence  in  time  it  diminishes  in  the  air  vessel,  and  some 

means  for  replenishing  it  has  to  be  provided.  Small 
valves  called  snifting  valves  have  been  adopted, 
but  they  are  not  always  effective.  The  air  is  in  the 
vessel  under  pressure,  and  to  get  any  more  air 
into  it  force  must  be  used.  In  this  ram  a  long, 
small  bore  pipe  H  is  connected  to  the  drive  pipe  A  ; 
it  has  a  valve  J  at  the  top  which  allows  air  to  enter, 
and  which  closes  when  the  pressure  comes  on  ;  the 
air  is  then  compressed  and  forced  into  the  air 
vessel,  a  small  quantity  at  each  pulse. 

In  Blake's  hydraulic  ram  (Fig.  105)  springs 
were  used  instead  of  air.  C  is  a  piston,  sliding 
water-tight  in  a  cylinder  and  held  down  by  a  lever 
and  springs  ;  the  water  entering  C  raises  it  up  at 
every  pulse,  and  thus  acts  regularly. 
Another  device,  by  Messrs.  Easton  &  Co.,  whereby  air  is  compressed  in  a  chamber 

in  connection  with  the  drive  pipe  and  some  of  it  carried  into  the  air  vessel,  is  shown 

in  Fig.  106.     When  the  pulse  valve  is  open,  and  the  water  flows  past  the  opening  F,  air 

fills  the  small  direct  connected  vessel  C  through  a  snifting  valve   D.     Upon  the  valve  B 


FlG.  105. — Spring-Balanced  Ram. 


Modern   Engines 


FIG.  106. — Double  Air  Vessel  Ram. 


closing,  some  of  the  water  forces  itself  into  C  and  some  into  the  smaller  vessel  F  ;  thus 

the  violence  of  the  compression  is  reduced  by 
the  air  spring  in  F,  which  forces  the  water 
back  again  through  D  into  C  with  air  ab- 
sorbed during  the  high  pressure. 

We  shall  only  refer  to  one  form  of  pump- 
ing ram.  This  machine  is  used  for  raising 
clean  water  from  a  well  by  means  of  a  fall 
from  a  river  or  drain  of  unclean  water. 
It  has  some  useful  applications,  but  is  no 
longer  a  simple  machine.  It  must  be  re- 
membered that  these  hydraulic  machines 
are  not  economical,  and  only  on  account  of 
their  simplicity  can  they  be  recommended. 
When  we  therefore  depart  from  a  simple 
construction  and  introduce  pistons,  rods, 
valves,  levers,  and  make  a  complicated 
mechanism  of  it,  the  advantages  disappear, 
and  we  may  well  consider  whether  a  turbine 
and  pump  would  not  in  the  circumstances  be 
better  for  the  purpose. 

Blake's  pumping  ram  is  shown  in  Fig. 
107.  In  this  pump  a  piston  C  is  driven  up  by 
the  recoil  of  the  drive  water.  On  the  other 

end  of  the  piston  rod  is  a  pumping  piston  D  ;  F  is  the  suction  pipe  into  the  well ;  H,  the 

delivery  water   valve 

into  receiver  K,  and 

J  is  the  rising  main. 

The  spring  forces  the 

pistons      back      into 

their  lowest  position 

between  each  pulse. 
In  the  same  way 

air     may     be     com- 
pressed  and   used  in 

rock  drills  and  other 

mining    tools.       And 

great  use  was  made 

of  hydraulic  ram  en- 
gines in  compressing 

air    for    driving    the 

tunnel  through  Mont 

Cenis,  water  being  un- 
limited in  quantity. 
In  setting  out  a 

hydraulic    ram    it    is 

necessary      first      to 

ascertain  the  quantity 

of  water  available  for 

the  drive,  and  to  sur- 
vey the  ground  to  ob-  FIG.  107.— Pumping  Hydraulic  Ram. 

tain  the  position  for 

the  ram  where  it  may  obtain  the  greatest  fall  through  a  pipe  of  at  least  30  feet  long.     It 


Hydraulic   Rams 


is  evident  that  a  long  pipe  will  be  required  for  a  high  lift,  for  the  force  at  the  moment  of 
closing  the  pulse  valve  is  proportional  to  the  mass  of  water  in  motion  in  the  drive  pipe 
and  to  its  rate  of  motion.  On  the  other  hand,  it  is  useless  to  make  the  pipe  too  long  ; 
for  while  a  long  pipe  gives  a  greater  pressure,  it  beats  slower  than  a  short  pipe.  In 
practice  the  length  of  the  drive  pipe  is  limited  often  by  the  nature  of  the  fall  and  the 
location  of  the  ram,  which  has  to  be  selected  for  the  running  off  of  the  tail  or  waste 
water.  The  shortest  length  is  about  five  times  the  height  of  the  fall,  and  where  possible 
it  may  be  increased  to  ten  times  the  height  of  the  fall. 

The  table  here  given  is  one  compiled  by  the  American  Engineer,  gives  the  coefficient 
for  various  quantities  of  available  drive  water,  which,  multiplied  by  the  coefficient  for 
any  given  height  to  which  the  water  is  to  be  forced,  will  give  the  quantity  delivered. 

Thus  if  we  had  a  2o-foot  fall  to  deliver  50  feet  high,  the  quantity  delivered  would 
be,  for  100  gallons  available  per  minute,  0.3282  x  100  =  32.82  gallons  delivered  per  minute. 

TABLE  VI.— ELEVATION. 


bo 

•11 
I1 

15 

18 

21 

24 

27 

3° 

35 

40 

45 

5° 

60 

70 

80 

90 

100 

Feet. 

2 

.O724 

•  OCTI 

.O4.2O 

.0^07 

.021"; 

.0181 

.OI  12 

.0067 

.OO27 

3 

*  v  /   T^ 

•1327 

ooo 

.1020 

T^ 
.0807 

o  / 

.0651 

oo 
•0530 

.0441 

.0326 

VWO 

•0243 

/ 

.0181 

•0132 

.0063 

.0017 

... 

4 

.1960 

•I535 

•1234 

.  IO2O 

.0854 

.0724 

.0560 

.0441 

.Q348 

.0281 

.0180 

.0112 

.0063 

.OO27 

5 

.2614 

.2068 

.1686 

.1404 

.1189 

.1020 

.0807 

.0652 

•0533 

.0441 

•0307 

.O2I7 

.0150 

.0099 

.0063 

6 

.3282 

.2614 

.2146 

.I800 

•  1535 

.1327 

.1063 

.0870 

.0724 

.0608 

.0441 

•0325 

.0243 

,0l8o 

.0132 

7 

.3960 

.3170 

.26l4 

.2203 

.1885 

.  1640 

•IS2? 

.  1096 

.0920 

.0782 

.0580 

.0441 

.0340 

.0264 

.0205 

8 

.4647 

•3733 

.3090 

.2614 

.2248 

.1960 

•1595 

.1327 

.1121 

.0960 

.0724 

.0560 

.0441 

•0351 

.0281 

9 

•5341 

•4303 

•3572 

•303° 

.2614 

.2285 

.1868 

.1561 

•I327 

.  1142 

.0870 

.0682 

•°545 

.0441 

.0360 

10 

.6040 

.4877 

.4058 

•345° 

.2984 

.2614 

.2145 

.1800 

•1535 

.1327 

.1020 

.0807 

.0651 

•°533 

.0441 

ii 

•6745 

•5459 

•4549 

•3874 

•3357 

.2947 

•2425 

.2041 

.1746 

•JSH 

.1172 

•0934 

.0760 

.0627 

.0524 

12 

•7453 

.6040 

•5043 

.4302 

•3733 

.3282 

.2708 

.2285 

.1960 

.1704 

.1327 

.1063 

.0870 

.0723 

.0608 

13 

.8166 

.6627 

•5540 

•4732 

.4112 

.3620 

.2994 

•2532 

.2177 

.1896 

.1483 

.1194 

.0983 

.0821 

.0604 

H 

.8881 

.7217 

.6040 

.5166 

•4494 

.3960 

.3282 

.2780 

•2395 

.2090 

.1640 

.1327 

.  1096 

.0920 

.0782 

IS 

.9600 

.7809 

•6543 

.5601 

.4877 

•4303 

•3572 

•3°3° 

.2614 

.2285 

.1800 

.1460 

.1211 

.1020 

.0870 

16 

.8404 

.7048 

.6040 

•5263 

.4647 

.3863 

.3282 

•2835 

.2482 

.1960 

•1595 

.1327 

.1121 

.0960 

17 

.9001 

•7555 

.6480 

•5650 

•4993 

•4157 

•3535 

•3058 

.2680 

•  2123 

•I731 

.1444 

.1223 

.1050 

18 

.9600 

.8064 

.6921 

.6040 

•534i 

•4451 

•3790 

.3282 

.2880 

.2286 

.1868 

.1561 

.1327 

.1142 

19 

•8574 

•7364 

.6430 

.5690 

.4746 

.4046 

•35°7 

.3081 

•2449 

.2006 

.1680 

.1430 

.1262 

20 

.9086 

.7808 

.6823 

.6040 

.5042 

•4303 

•3733 

.3282 

.2614 

•  2145 

.I80O 

•'535 

.1327 

21 

.9600 

.8254 

.7217 

.6392 

•5340 

.4561 

.3960 

.3486 

.2780 

.2286 

.I92O 

.1640 

.1420 

22 

.8701 

.7612 

•6745 

.5640 

.4820 

.4188 

.3688 

•2947 

•2425 

.2041 

.1746 

•  1514 

23 

.9150 

.8007 

.7098 

•5940 

.5080 

.4417 

.3892 

•3"4 

.2567 

.2163 

•1853 

.1609 

24 

.9600 

.8404 

•7453 

.6241 

•534i 

•4657 

.4097 

.3282 

.2708 

•2l85 

.1960 

.1704 

The  old  rule  for  finding  the  diameter  of  the  drive  pipe  D=  \/(i-63Q),  Q  being  the 
available  amount  of  water  in  cubic  feet ;  and  if  h  —  the  height  to  which  the  water  is  to  be 

lifted  and  H  the  fall,  then  L,  the  length  of  the  drive  pipe,  should  be  L=H+^  +  —  X2. 

ri 

In  the  case  just  taken,  H  =  20,  h  =  50  ;  then  L  =  20 +  50 +  £5x2  feet  =  145  feet. 

20 

The  capacity  of  the  air  vessel  should  be  equal  to  the  capacity  of  the  drive  pipe,  and 
the  area  of  the  opening  of  the  pulse  valve  should  be  nearly  the  area  of  the  drive  pipe  in 
section  ;  per  100  gallons,  D  would  be=  ^(1.63  x  i6)  =  5  inches  nearly. 

The  air  vessels  are  usually  cast  iron,  well  pitched  inside  to  fill  any  pores  up  through 
which  air  might  escape.  Glass  has  also  been  used  for  small  pumps. 

Hydraulic  rams  require  to  have  well  made  and  well  designed  valves,  and  occasional 
attention  to  see  that  the  air  is  sufficient  in  the  air  vessel.  In  country  houses  they  are 
much  used  in  all  countries  to  provide  a  household  water  supply  under  pressure. 

We  now  may  consider  other  fluid-on-fluid  pressure  engines,  in  which  gases  act.  upon 
liquids  and  vice  versa. 


86  Modern   Engines 

STEAM  JETS 

The  air  spray  is  familiar  to  every  one,  and  illustrates  the  production  of  a  partial 
vacuum  produced  at  right  angles  to  a  jet  of  fluid.  We  have  many  interesting  applica- 
tions of  this  principle  in  engineering. 

The  acting  part  in  these  apparatus  is  a  jet  of  air,  steam,  or  water,  which  inducts 
motion  in  a  surrounding  mass  of  fluid.  In  the  simple  cross  blast  jet  the  horizontal 
jet  passing  across  the  mouth  of  the  vertical  pipe  acts  simply  by  cutting  off  the  atmo- 
spheric pressure  from  that  mouth,  and  so  the  liquid  rises  in  the  vertical  tube  and  is 
blown  away  as  a  spray.  The  velocity  of  the  jet  of  air,  or  steam,  or  water  is  sufficient 
to  carry  it  across  the  mouth  of  the  tube  without  deflection,  even  although  there  is  a 
vacuum  beneath. 

In  the  same  way  the  jet  acts  in  nozzles.  Here  the  velocity  of  the  jet  first  carries 
air  out  of  the  annular  space,  making  a  partial  vacuum  into  which  the  liquid  rushes  ;  the 
liquid  coming  in  contact  with  the  jet  is  carried  on  also  by  contact. 

As  nozzles  are  the  important  organs  of  these  induction  machines  called  injectors 
and  ejectors  working  on  these  principles,  we  must  consider  nozzles,  or  hollow  cones,  in 
various  types. 

A  converging  cone  delivers  a  rod  of  fluid  without  contraction  to  the  same  extent 
as  a  straight  tube  or  through  a  hole  in  a  plate. 

Steam  being  the  most  important  fluid  at  present,  and  more  information  being 
collected  regarding  it  than  about  other  gases,  we  will  first  consider  the  steam  jet. 

Experiments  have 
been  made  with  a  conical 
nozzle,  as  shown  in  Fig. 
108.  This  nozzle  may  be 
-used  with  either  end  as 
the  inlet  and  the  other  end 
the  outlet. 

With  the  wide  end  as 
FIG.  108.— De  Laval  Steam  Nozzle.  ,       .    ,    ,          ,   A, 

the  inlet  and  the  narrow 

end  the  outlet,  we  get  the  fluid  gradually  increasing  in  velocity  up  to  the  narrow 
exit,  where  it  issues,  slightly  converging  at  the  full  speed  due  to  the  height  or 
pressure. 

If  we  reverse  the  nozzle  we  get  a  very  different  result. 

Suppose  we  consider  the  nozzle  connected  to  a  steam  boiler  at  200  Ibs.  pressure 
about  atmospheric,  or  214.7.  According  to  Professor  Zeuner,  in  a  nozzle  in  which  steam 
is  adiabatically  expanded  the  potential  energy  (heat)  is  converted  into  kinetic  energy. 
The  kinetic  energy  of  i  Ib.  of  steam  at  velocity  V  in  feet  per  second  is  of  course 

equal  to—  V2  r  ,  , 

—  foot-lbs.     (i) 

2g 

Suppose  steam  is  let  down  from  pressure  p±  to  pressure  /2  adiabatically  in  an 
expanding  nozzle.  The  internal  heat  of  the  steam  at  pl  =  (the  internal  heat  of  the  steam 
at  /2)  + (kinetic  energy  at  pz  in  heat  units)  ;  or,  in  other  words,  the  kinetic  energy  is 
proportional  to  H  -  h,  where  H  is  the  internal  heat  at  pl  and  h  that  at  py  And  if  J  is 
the  mechanical  equivalent  of  heat,  the  velocity  of  the  steam  acquired  by  the  time  it  had 
fallen  to  p.2  would  be—  V  =  *j2g](U.-h).  (2) 

The  internal  heats  depend  on  the  percentage  of  moisture  in  the  steam,  calculated 
on  the  assumption  of  constant  entropy  during  the  expansion. 

Theory  and  experiment  agree  that  at  a  certain  ratio  between  p^  and  p.,  a  maximum 
amount  of  steam  flows  through  a  converging  nozzle.  This  limiting  ratio  is — 

~~  =  °-  577  J  and  hence  p.,  =  o.  577  x  pr 
P\ 


160  - 


tea  -| 


130}-\ 


At 

Section 
B. 


"itofygauge 


Flow  of  Fluids  in  Nozzles 


In  the  case  cited  ot  a  pressure  pl  equal  to  214.7  absolute  ;  pv  that  is  at  section  B  of 
the  nozzle,  the  pressure  would  equal  0.577  x  214.7=  124  Ibs.     (3) 
Absolute  whichever  end  of  the  nozzle  we  used  as  the  inlet,  or  109.2  gauge  pressure. 

The  steam,  therefore,  which  escapes  from  section  B  has  still  much  pressure,  and 
this  can  be  seen  by  making  the  large  end  the  inlet  and  blowing  the  steam  into  the 
atmosphere,  when  the  issuing  jet  will  be  seen  to  instantly  expand  widely. 

By  using  the  nozzle  at  the  narrow  end  as  the  inlet,  the  steam,  after  passing 
section  B,  is  constrained  to  flow  forward  at  a  still  increasing  velocity  as  its  pressure 
falls,  until  it  reaches  the  out- 
let, where  it  cannot  expand 
further,  and  issues  as  a  cylin- 
drical jet  at  the  full  velocity 
due  to  the  pressure  differ- 
ence. 

Professor  Jamieson  has 
plotted  out  the  following 
curves  (Fig.  109)  of  the  expan- 
sion in  his  contribution  to  the 
discussion  on  the  De  Laval 
steam  turbine,  with  a  view 
of  explaining  not  only  the 
sudden  fall  of  pressure  near  to 
and  in  the  throat  of  the  steam 
nozzle  of  the  De  Laval  turbine, 
but  also  the  further  fall  ot 
pressure  along  the  conical  part 
to  its  mouth.  The  full  line 
curve  represented  the  natural 
loss  of  pressure  in  dry  satur- 
ated steam  as  it  expanded 
in  accordance  with  Professor 
Rankine's  well-known  formula 
pv\^  =  a  constant ;  where  p 
was  the  pressure  in  Ibs.  per 
square  inch  absolute,  and  v 
the  corresponding  volume  in 
cubic  feet  per  Ib.  of  steam. 
This  curve  is  drawn  from  475 
Ibs.  per  square  inch — at  which 
pressure  i  Ib.  of  the  steam 
occupied  i  cubic  foot — down 
to  i  Ib.  absolute,  at  which 
it  occupied  330  cubic  feet. 
In  the  Figure  is  included  the 

range  of  pressures  specially  mentioned  in  the  paper.  The  dotted  line  represented 
an  adiabatic  expansion  curve  to  pv^~  =  a  constant,  from  215  Ibs.  absolute  at  Section 
A,  before  entering  the  nozzle,  down  to  0.93  Ib.  at  Section  C,  where  it  occupied 
256.8  cubic  feet,  and  left  the  nozzle  with  a  velocity  of  4127  feet  per  second  with 
24  per  cent,  of  moisture.  This  curve  passed  through  the  point  B,  where  the 
steam  occupied  3.5  cubic  feet,  and  has  4  per  cent,  of  moisture,  with  a  velocity  of 
1500  feet  per  second.  Now,  it  was  evident  from  this  curve  that  if  the  potential 
energy  of  each  Ib.  of  static  steam  at  A  had  been  so  far  converted  into  kinetic  energy 
at  B  that  it  had  there  a  velocity  of  1500  feet  per  second,  and  contained  4  per  cent. 


60 


At 

Section 
A. 

Pressure  per  square  inch\ 
in  Ibs.  absolute   .         .  / 

Pressure  per  square  inchn 
in  Ibs.  absolute  above  Vaoo 
atmosphere          .         .  J 

Per  cent,  of  moisture         .  o 

Volume  of  steam  in  cubic  \ 
feet  per  Ib.  .         .         . ) 

Velocity  in  feet  per  second    o 

The  black  line  curve  


4 

3-5 
1500 


At 

Section 
C. 

0-93 


24 

256.8 
4127 


represents  the 

expansion  curve  of  dry  saturated  steam  to 
=  constant. 


a* 


The   dotted  line   curve represents 

the  adiabatic  expansion  of  steam  as  per  the 
above  data  in  the  De  Laval  turbine  steam 
nozzle  to  6v\P-= constant. 


•MlJk. 


eo     vo    eo     oo     too  *xo  sso   *to  aaoasss&o 
VOLUMES  IN  .CUBIC  FCET  TO  THE  LB. 


FIG.  109. — Comparison  of  Data  and  Curve  from  the  De  Laval 
Nozzle,  with  the  Natural  Expansion  Curve  for  Dry  Saturated 
Steam. 


88 


Modern  Engines 


of  moisture,  with  an  increase  of  volume  from  2.11  cubic  feet  at  A  to  3.5  cubic  feet 
at  B  it  must  of  necessity  have  fallen  in  pressure  from  215  to  125  Ibs.  absolute  pres- 
sure in  doing  so.  This  is  in  strict  accordance  with  the  natural  law  for  the  adiabatic 
expansion  of  steam.  The  temperature  of  the  steam  must  also  have  fallen  from 
382°  Fahr.  to  at  least  340°  Fahr.  in  this  short  passage.  It  might  be  that  the  steam  in 
passing  from  A  to  B,  and  from  the  very  small  throat  of  ^-inch  diameter,  at  the  rate  of 
8  Ibs.  weight  per  second,  naturally  formed  a  vena  contmcta  due  to  "throttling."  In 
any  case,  it  must  there  lose  potential  energy  due  to  friction  and  increased  velocity. 
This  would  account  for  its  expansion  from  i  Ib.  of  dry  saturated  steam  at  A  to  that  of 
slightly  moist  steam  at  B,  with  a  corresponding  and  natural  loss  of  pressure  in  temper- 
ature during  its  increase  of  velocity  from  o  to  1500  feet  per  second  from  A  to  B,  and 
corresponding  fall  in  pressure. 


TABLE  VII.— THE  VELOCITY  OF  OUTFLOW  AND  THE  WORKING  CAPACITY  OF 
DRY  SATURATED  STEAM   FROM  EXPANDING  CONES. 

KONRAD  ANDERSSON. 


Counter-pressure  i  Atmosphere. 

Counter-pressure  2.4  Lbs.  per  Square 
Inch  Absolute,  corresponding  to 

Counter-pressure  0.93  Lbs.  per  Square 
Inch  Absolute,  corresponding  to 

25  Inch  Vacuum. 

28  Inch  Vacuum. 

Initial 

Steam 

Pressure, 
Lbs.  per 
Square 
Inch. 

Velocity 
of  Outflow 
of  Steam, 

Kinetic 

Energy 
Foot-lbs. 
per  Second. 

H.P.  of 

550  Foot-lbs. 
per  Second. 

Velocity 
of  Outflow 
of  Steam, 

Kinetic 
Energy 
Foot-lbs. 
per  Second. 

H.P.  of 

550  Foot-lbs. 
per  Second. 

Velocity 
of  Outflow 
of  Steam, 

Kinetic 
Energy 
Foot-lbs. 
per  Second. 

H.P.  of 

550  Foot-lbs. 
per  Second. 

Feet  per 

Feet  per 

Feet  per 

Second. 

Second. 

Second. 

Per  Lb.  of  Steam  per  Hour. 

Per  Lb.  of  Steam  per  Hour. 

Per  Lb.  of  Steam  per  Hour. 

60 

2421 

25.29 

0.046 

3320 

47-57 

0.087 

3680 

58.44 

o.  106 

80 

2595 

29.06 

0.053 

3423 

50-56 

0.092 

'3793 

62.08 

0.113 

100 

2717 

31.86 

0.058 

3520 

53-47 

0.097 

3871 

64.66 

0.118 

1  20 

2822 

34-37 

0.062 

3596 

55-8o 

O.  IOI 

394° 

66.99 

0.  122 

140 

2913 

36.62 

O.o66 

3661 

57-84 

0.105 

3999 

69.01 

0.125 

160 

2992 

38-63 

0.070 

3718 

59-65 

0.108 

4°45 

70.61 

0.128 

180 

3058 

4°-35 

0.073 

3764 

61.14 

O.  Ill 

4091 

72.22 

O.I3I 

200 

3"5 

41.87 

0.076 

38lO 

62.64 

0.114 

4127 

73-50 

0.134 

220 

3166 

43.26 

0.079 

3852 

64.03 

o.  116 

4J59 

74.64 

0.136 

280 

3294 

46.83 

0.085 

3962 

67.74 

0.123 

4229 

77.18 

0.140 

In  Mr.  Konrad  Andersson's  paper  he  gives  an  example  of  the  action  of  the  steam  in 
the  expanding  nozzle, — the  narrow  end  connected  to  boiler  at  200  Ibs.  pressure,  the  wide 
end  into  a  28  inch  vacuum,  steam  supposed  to  enter  dry. 

The  general  formula?  for  the  velocity  of  a  gas  in  feet  per  second  due  to  a  difference 
of  pressure  is  V=  ^2.  gh,  where  h  is  the  height  of  a  column  of  the  gas  whose  weight 
balances  the  difference  of  pressure.  But  this  formulae  has  its  limitations,  for  beyond  a 
difference  of  pressure  less  than  58  per  cent,  of  the  initial  pressure  the  flow  is  constant. 
The  velocity  of  the  discharge  of  steam  from  a  boiler  at  100  Ibs.  pressure  is  no  greater 
into  a  vacuum  than  it  is  into  another  boiler  at  58  Ibs.  pressure. 

But  this  is  true  only  for  a  converging  nozzle  discharging  at  the  narrow  end, 
and  suddenly  and  unrestrainedly  expanding ;  if,  however,  the  nozzle  is  prolonged  and 
gradually  diverges,  the  velocity  increases  and  becomes  proportional  to  the  differ- 
ence of  pressure  between  the  narrow  nozzle  and  the  wide  end.  The  final  velocity 
of  the  steam  is  acquired  in  two  stages.  First,  it  acquires  a  velocity  of  1500  feet 
per  second  in  passing  from  the  boiler  to  and  through  the  converging  parts,  and  a  further 
2627  feet  in  expanding  in  the  diverging  part  of  the  nozzle,  making  a  final  velocity  of 
4127  feet. 


Flow  of  Steam 


TABLE  VIIL— PROPERTIES  OF  STEAM. 


Absolute 
Boiler  Pres- 
sure per 
Square  Foot. 

Absolute 
Boiler 
Pressure 
per  Square 

Tnrh 

Volume  of 
i  Lb.  of 
Steam. 
Cubic  Feet. 

Weight  of 
i  Cubic  Foot 
of  Steam. 
Lbs. 

Temperature 
of  Steam. 
0  Fahr. 

Velocity  of 
Steam  Jet, 
calculated 
from  Narrow 
Nozzle.    Feet 

Square  Root 
of  Product 
of  Density 
x  Pressure 
per  Square 

J.liV«ll. 

per  Second. 

Foot. 

144 

I 

330.4 

.0030 

102.8 

1238 

.6 

288 

2 

171.9 

.0058 

126.3 

1262 

!-3 

432 

3 

i  '7-3 

.0085 

141.6 

1277 

1.9 

576 

4 

89.51 

.0112 

i53-i 

1291 

2-5 

720 

5 

72.56 

.0138 

162.4 

1299 

3-i 

1,440 

IO 

37-83 

.0264 

J93-3 

1326 

6.2 

2,160 

15 

25-85 

.0386 

213.0 

9.2 

2,880 

20 

19.74 

.0506 

227.9 

12.  1 

7,200 

5° 

8-333 

.1199 

280.9 

1398 

29.4 

10,080 

70 

6.076 

.1645 

302.7 

40.1 

11,520 

So 

5-358 

.1866 

311.8 

44-8 

12,960 

9° 

4.796 

.2085 

320.1 

52.0 

14,400 

100 

4-342 

.2302 

327.6 

1420 

58.0 

15,840 

no 

3-969 

.2519 

334-6 

63.2 

17,280 

1  20 

3-656 

•2735 

341.0 

69.0 

18,720 

130 

3-390 

•2949 

347-1 

74-° 

20,160 

140 

3.161 

•3J63 

352.8 

80.0 

21,600 

150 

2.962 

•3376 

358.2 

'434 

S6.o 

23,040 

160 

2.786 

•3568 

363-3 

91.0 

24,480 

170 

2.631 

.3800 

368.2 

... 

96.0 

25,920 

180 

2-493 

.4012 

372.8 

... 

IO2.2 

27,360 

190 

2.368 

.4223 

377-3 

IO8.O 

28,800 

200 

2.256 

•4433 

381.6 

J452 

112.  1 

36,000 

250 

1.825 

.5478 

400.8 

1454 

140.4 

Taking  the  three  sections  of  the  cones  : — 

Section  A — 

Pressure,  200  Ibs.  above  atmosphere. 

Moisture  percentage  =  o. 

Unit  quantity  of  steam,  i  Ib. 
Section  B  (smallest  section) — 

Pressure,  no  Ibs. 

Quantity  of  steam,  0.96.     Moisture,  0.4  Ibs. 

Velocity  V=  \/2^J(H-A)=  1500  feet  per  second. 

Volume  of  steam,  3.5  cubic  feet. 
Section  C  (the  wider  end) — 

Pressure,  2  inches  of  mercury  (absolute  pressure). 

Percentage  of  moisture  in  the  steam,  24  per  cent. 

Specific  quantity  of  steam,  0.76. 

Velocity  of  the  steam,  4127  feet  per  second. 

Specific  volume  of  the  steam,  256.8  cubic  feet  per  Ib. 

The  proportion  between  the  areas  of  the  large  and  small  section  of  this  nozzle  should 
be  as  27.2345  to  i,  or  the  proportion  between  the  diameters  of  these  two  sections  as 
5.2187  to  i.  If,  for  instance,  the  diameter  of  the  small  section  is  6  millimetres,  or  very 
nearly  £  of  an  inch,  the  diameter  of  the  large  section  should  be  31.31  millimetres,  or 
nearly  i^  inch.  Through  such  a  nozzle  there  passes  a  certain  constant  weight  of  dry 
saturated  steam  of  200  Ibs.  pressure  per  hour,  neither  more  nor  less.  This  fact  of  the 
nozzle  passing  only  a  certain  amount  of  steam  per  hour  is  used  as  a  measure  of  steam. 

The  quantity  of  steam  passed  by  the  nozzle  is  measured  by  the  section  B,  and  is 
equal  to  Q  =  370  AD  so  long  as  the  difference  of  pressure  is  greater  than  f  the  initial 


9° 


Modern   Engines 


pressure.  A  is  the  area  of  the  section  at  B,  and  D  the  weight  of  i  cubic  foot  at  215 
absolute  pressure  ;  hence  370  x  0.25"  x  0.5  =462.5  Ibs.,  taking  A  as  £  inch  and  i  cubic  foot 
of  steam  at  that  pressure  =  0.5  Ibs.  weight  approximately. 

W  x  V 

We  have  seen  that  the  impulse  per  second  of  a  fluid  is  equal  to .     From  this 

<T 

V2 
we  can  proceed  to  find  the  impulsive  power  of  a  jet.     Its  kinetic  energy  =  —  in  foot-lbs. 

2g 

Say  it  issues  from  an  expanding  cone  at  4000  feet  per  second,  then  the  horse-power  per 
Ib.  of  steam  would  be 

40oo2 

=  6T4x55ox36oo  =  0-I25  horse-Power  total 
impulsive  energy  per  Ib.  of  steam. 

But  if  the  steam  strikes  a  solid  body  or  a  liquid  body,  its  whole  kinetic  energy  is  not 
obtained.  In  a  steam  turbine  the  steam  leaves  the  buckets  with  about  a  third  of  its 
velocity  still  in  it.  When  it  strikes  water,  as  in  an  injector,  a  large  quantity  of  its  energy 
merely  heats  the  water. 


All  that  is  known  in  the 


INJECTORS 

We  now  come  to  consider  the  nozzles  and  their  action, 
actual,  design  of  injectors, 
ejectors,  and  kindred  ma- 
chines have  been  found  by 
experiment.  We  can,  as  we 
have  just  seen,  calculate  the 
efflux  of  a  fluid  from  an 
orifice,  find  its  quantity  and 
velocity  if  we  know  the  im-  Fie.  no.— Simple  Nozzle, 

pelling  pressure  or  head  ;  and 
if  we  know  this  and  want  to  find  the  area  of  an  orifice  to  deliver  a  certain  quantity 


FIG.  in. — Experimental  Nozzle. 


FIG.  112. — Filter  Pump. 


Induction  of  Fluid  Flow 


91 


per  second,  we  can  also  find  that  dimension.  For  the  rest,  we  must  depend  upon 
experience.  The  fluid  friction  is  reduced  by  tapering  the  nozzles  ;  hence  the  tapers  are 
of  interest. 

Consider  Fig.  1 10,  say,  i  square  inch  wide  at  the  entrance  A,  and  ^  square  inch  at 
the  throat  C.  Fluids  liquid  like  water  have  considerable  inertia,  hence  cannot  without  loss 
be  started  into  quick  motion  in  short  time.  The  velocity  of  the  water  in  the  nozzle  at  C 
would  be,  we  know,  =  8  *Jh,  where  h  is  the  head  corresponding  to  the  pressure  at  C. 
Suppose  the  velocity  at  C=  100  feet  per  second,  the  section  of  C  is  equal  to  ^  the  section 
at  A  ;  hence  the  velocity  at  A  will  be  10  feet  per  second,  and  from  that  to  B  the  same. 
At  B  the  section  begins  to  lessen  and  the  velocity  to  increase,  and  the  longer  the  cone 


..i 


FIG.  113. — Exhauster  and  Compressor. 


FIG.  114. — Filter  Pump  Nozzle. 

from  B  to  C  the  more  gradual  will  the 
increase  of  velocity  be.  The  velocity 
for  water  at  A  should  not  exceed  3  feet 
per  second.  The  axial  distance  from 
B  to  C  should  not  be  less  than  twice 
the  diameter  at  B  for  water. 

A  simple  cone  like  this  is  em- 
ployed only  for  throwing  water,  steam, 
or  gases  to  a  distance  in  a  desired 
direction. 


In  Fig.  45  (p.  39)  we  showed  that  the  pressure  falls  as  the  velocity  increases,  and 
vice  versft,  in  a  fluid  flowing  through  the  pipes  at  different  sectional  areas.  This  can 
also  be  shown  for  steam  or  air  by  an  experiment  as  shown  in  Fig.  in,  in  which  a 
bi-conical  nozzle  with  small  tubes  at  right  angles  to  the  axis  is  set  up.  The  tubes  dip 
into  water  or  mercury  some  feet  below  the  nozzle.  On  blowing  air  or  steam  through  it 
is  found  that  a  partial  vacuum  is  formed  at  the  mouth  of  the  tubes,  and  the  amount  of 
the  vacuum  may  be  measured  by  the  height  to  which  the  liquid  is  sucked  up  into  the 
tubes.  The  height  will  be  greatest  where  the  velocity  of  flow  is  greatest,  that  is  at  B 
and  onwards.  On  this  principle  of  suction  many  useful  appliances  are  made,  notably 
little  exhausters  for  chemical  work,  one  of  which  is  shown  in  Fig.  112  for  attaching  to 
an  ordinary  water  tap.  The  flowing  water  carries  air  with  it  and  produces  a  vacuum  in 
any  vessel  attached  to  the  side  pipe.  It  may  also  be  used  to  produce  air  pressure,  for 


92  Modern   Engines 

the  water  will  carry  the  air  into  a  receiver  against  considerable  pressure.  In  order  to  do 
this  the  arrangement  shown  in  Fig.  113  is  made.  The  nozzle  is  prolonged  and  expanded 
trumpet  shaped  and  fixed  airtight  into  a  large  receiver  with  an  overflow.  The  pressure 
at  which  the  air  will  be  delivered  will  depend  upon  the  height  to  which  this  overflow 
is  carried.  Fig.  1 14  shows  the  nozzle  separate  on  a  large  scale. 

HYDRAULIC  AIR  COMPRESSOR 

It  is  worthy  of  note  that  a  large  machine  on  this  same  principle  has  been  designed 
and  put  into  practice  at  a  place  called  Magog  in  Canada.  Instead  of  one  side  entrance 
for  air,  a  great  number  of  small  pipes  are  let  into  the  flowing  water,  just  where  it  has 
acquired  full  velocity  due  to  the  height  of  the  waterfall.  It  is  the  invention  of  Mr.  Taylor 
of  Montreal.  The  following  is  a  description  referring  to  the  Fig.  115. 

The  letters  on  the  figure  are  references  to  the  parts  as  follows : — 

A,  penstock  or  water  supply  pipe. 

B,  receiving  tank  for  water. 

C,  compressing  pipe. 

D,  air  chamber  and  separating  tank. 

E,  shaft,  or  well,  for  return  water.     (The  required  pressure  is  proportional  to 

the  depth  of  the  water  in  this  shaft.) 

F,  tail  race  for  discharge  water. 

G,  timbering  to  support  earth. 
H,  blow-off  pipe. 

I,  compressed  air  main. 

J,  head  piece,  consisting  of — 

a,  telescoping  pipe,  with 

b,  bell-mouth  casting  opening  upwards. 

c,  cylindrical  and  conoidal  casting. 

d,  vertical  air  supply  pipes.      (Each  pipe  has  at  its  lower  end  a  number 

of  smaller  air  inlet  pipes  branching  from  it  towards  the  centre  of  the 
compressing  pipe.) 

e,  adjusting  screws  for  varying  the  area  of  water  inlet. 

f,  hand  wheel  and  screw  for  raising  the  whole  head  piece. 
K,  disperser. 

L,  apron. 

M,  pipes  to  allow  of  the  escape  of  air  from  beneath  apron  and  disperser. 

N,  legs  by  which  the  separating  tank  is  raised  above  the  bottom  of  the  shaft  to 

allow  of  egress  of  water. 
P,  automatic  regulating  valve. 

WORKING  OF   THE   COMPRESSOR 

The  water  is  conveyed  to  the  tank  B  through  the  penstock  A,  where  it  rises  to  the 
same  level  as  the  source  of  supply.  In  order  to  start  the  compressor  the  head  piece  J 
must  be  lowered  by  means  of  the  hand  wheel  f,  so  that  the  water  may  be  admitted 
between  the  two  castings  b  and  c.  The  supply  of  water  to  the  compressor,  and  con- 
sequently the  quantity  of  compressed  air  obtained,  is  governed  by  the  depth  to  which 
the  head  piece  is  lowered  into  the  water.  The  water  enters  the  compressing  pipe 
between  the  two  castings  b  and  c,  passing  among,  and  in  the  same  direction  as,  the 
small  air  inlet  pipes.  A  partial  vacuum  is  created  by  the  water  at  the  ends  of  these 
small  pipes,  and  hence  atmospheric  pressure  drives  the  air  into  the  water  in  innumerable 
small  bubbles,  which  are  carried  by  the  water  down  the  compressing  pipe  C.  During 
their  downward  course  with  the  water  the  bubbles  are  compressed,  the  final  pressure 
being  proportional  to  the  column  of  return  water  sustained  in  the  shaft  E  and  tail  race  F. 


Hydraulic  Air  Compression 


93 


The  diagram  Fig.    116  shows  the  relative  sizes  of  the  bubbles  as  they  descend  in  a 
compressing-  pipe  of  1 16  feet  in  length. 

When  they  reach  the  disperser  K  their  direction  of  motion  is  changed,  along  with 
that  of  the  water,  from  the  vertical  to  the  horizontal.  The  disperser  directs  the  mixed 
water  and  air  towards  the  circumference 
of  the  separating  tank  D.  Its  direction 
is  again  changed  towards  the  centre  by 
the  apron  L.  From  thence  the  water 
flows  outward,  and,  free  of  air,  passes 
up  the  lower  edge  of  the  separating  tank. 
During  this  process  of  travel  in  the 
separating  tank,  which  is  slow  compared 
with  the  motion  in  the  compressing  pipe 
C,  the  air  by  its  buoyancy  has  been 
rising  through  the  water  and  pipes  M,  M, 
from  under  the  apron  and  disperser,  to 
the  top  of  the  air  chamber  D,  where  it 
displaces  the  water.  The  air  in  the 
chamber  is  kept  under  a  nearly  uniform 
pressure  by  the  weight  of  the  return  water 
in  the  shaft  and  tail  race. 

The  air  is  conveyed  through  the 
main  I,  up  the  shaft  to  the  automatic 
regulating  valve  (of  which  a  diagram  is 
given),  and  from  thence  to  the  engines, 
etc.  The  air  pressure  in  the  main  and 
air  chamber  increases  i  Ib.  per  square 
inch  for  each  2  feet  3^  inches  that  the 
water  is  displaced  downwards  in  the  air 
chamber  by  the  accumulating  air.  The 
variation  in  pressure  from  this  source 
will  not  be  more  than  3  Ibs.  per  square 
inch  in  a  working  plant.  As  the  auto- 
matic valve  requires  a  change  of  only  i 
Ib.  per  square  inch  pressure  to  close  it 
completely,  it  will  be  evident  that,  by 
properly  adjusting  the  valve,  some  air  can 
always  be  retained  in  the  air  chamber, 
and  that  the  water  can  be  prevented  from 
ever  reaching  the  inlet  to  the  air  main. 
If  a  large  quantity  of  air  has  accumulated 
in  the  chamber  the  valve  allows  of  its 
free  passage  along  the  main  ;  but  when 
the  air  is  being  used  more  quickly 
than  it  is  accumulating,  and  the  pres- 
sure decreases  below  a  certain  point  FIG.  115.— Hydraulic  Air  Compressor, 
because  the  chamber  is  nearly  emptied 

of  air,  the  valve  shuts  partially,  or  completely,  adjusting  itself  to  the  supply  from  the 
compressor. 

When  the  air  has  displaced  the  water  almost  to  the  lower  end  of  the  compressing 
pipe  it  escapes  through  the  blow-off  pipe  H. 

In  the  hydraulic  air  compressor  a  bubble  of  air,  while  passing  down  the  compress- 
ing pipe,  is  kept  cool  by  the  body  of  water  surrounding  it.     The  process  of  compression 


94 


Modern  Engines 


ATMOSPHERE:  . 


e 

CO 


CD 


O 


o 


CD 


CD 


.  -l. 


is  comparatively  slow,  occupying1  from  15  to  25  seconds.  The  temperature  of  the  water 
is  scarcely  affected  by  the  heat  which  it  receives  from  the  air  during"  compression  (the 
heat  required  to  raise  i  cubic  foot  of  water  from  one  temperature  to  any  other  being 
about  3500  times  as  much  as  that  necessary  to  produce  the  same  change  of  temperature 
with  i  cubic  foot  of  air).  The  bubble  of  air  is  compressed  at  a  constant  temperature 

(i.e.  isothermally),  the  temperature  being  that 
of  the  water,  and  the  excess  of  moisture,  caused 
by  the  gradually  increasing  pressure,  is  de- 
posited on  the  walls  of  the  bubble.  Thus  it 
is  evident  that  the  air  is  collected  in  the  separat- 
ing tank  at  the  low  temperature  of  the  water, 
and  as  dry  as  it  is  possible  to  obtain  it.  By  a 
test  made  by  Professor  C.  H.  M'Leod,  Ma.  E., 
of  M'Gill  University,  on  50  cubic  feet  of  air 
hydraulically  compressed  to  52  Ibs.  gauge  pres- 
sure, it  was  found  that  the  expanded  air  con- 
tained only  i  of  the  vapour  usually  contained 
in  the  atmosphere  during  fine  weather  (or  14 
per  cent,  of  saturation).  This  test  was  made 
while  the  compressor  was  delivering  through 
the  main  1500  cubic  feet  of  air  per  minute. 

On  2oth  and  2ist  March  1897  a  pair  of 
7  inch  x  10  inch  engines  were  run,  under  a 
full  load,  by  the  air  delivered  direct  from  the 
compressor,  without  preheating,  for  40  hours 
continuously,  without  showing  any  sign  of 
a  moisture  deposit  on  the  interior  of  the 
exhaust. 

At  the  same  time  the  considerable  fall  in 
temperature  from  the  expanding  air  was  such 
as  to  produce,  by  condensation  of  the  atmo- 
spheric moisture,  a  heavy  coating  of  ice  on  the 
outside  of  the  exhaust  pipe. 

The  principles  are  simple.  Referring  to  Fig. 
1 13,  the  water  will  flow  from  the  height  A  to  B 
with  a  velocity  proportional  to  8VA  -  friction  ; 
the  air  drawn  in  will  pass  down  with  the  water 
so  long  as  the  velocity  of  the  water  is  greater 
than  that  of  a  bubble  of  air  liberated  at  the 
bottom  of  the  pipe,  with  the  column  of  water 
at  rest.  This  velocity  is  small,  being  less  than 
that  due  to  a  head  of  4  feet  of  water,  being 
about  8  feet  per  second  ;  hence  a  low  fall  will 
give  sufficient  velocity  to  the  water  to  enable  it 
FIG.  n6.-Compression  of  Air  Bubble  in  to  c  down  the  entangled  air. 

Compression  Pipe.  _,  „ ,          .     .     , .     ,    ,  ^, 

The  pressure  on  the  air  is  that  due  to  the 

head  BC,  Fig.  113,  so  that  we  obtain  higher  pressure  by  sinking  the  vessel  E  in  order 
to  increase  height  CB. 

There  is  a  limit  to  the  depth  E  may  be  sunk  for  any  given  head  BA,  depending 
upon  the  work  lost  in  friction,  agitation  of  the  water,  and  air.  And  air  is  absorbed  by 
the  water,  so  that  a  considerable  quantity  is  carried  up  the  exhaust  pipe  and  lost. 
Nevertheless  it  is  a  simple  and  useful  machine,  and  will  find  applications  in  lands  where 
waterfalls  abound. 


OOWKMTIVC 
VOLUMES 

GAUGE 
PRESSURE 

1-0000 

«. 

5LBS. 

'5966 

to 

•4949 

« 

~* 

20 

•3288 

SO 

•s&s?' 

„ 

Mr 

40 

•2462 

43 

«» 

CO 

Injectors 


95 


In  these  applications  the  fluids  act  by  suction.  In  another  class  there  is  this  same 
suction  principle,  and  also  another  principle  at  work,  in  which  a  moving-  jet  of  fluid 
moving"  through  another  body  of  fluid  induces  motion  therein,  and  the  moving  jet 
carries  an  annular  body  of  fluid  with  it,  and  gives  it  velocity.  On  this  principle  Sir  W. 
Siemens  made  an  exhaust  air  ejector  worked  by  steam.  In  order  to  give  the  steam  jet  a 
maximum  of  contact  with  the  air  to  be  set  in  motion,  he  made  the  steam  jet  a  thin  tube 
of  steam  produced  between  two  converging  nozzles.  The  air  flows  into  a  central  nozzle 
and  also  into  an  outer  nozzle,  as  shown 
in  Fig.  117,  so  that  there  is  a  tube  of  air 
outside  of  the  steam  tube  and  a  rod  of 
air  inside  the  steam  tube.  The  combined 
air  and  steam  flow  away  through  an 
expanding1  tube,  and  so  come  to  rest 
outside.  As  an  example  of  its  ejecting 
powers,  a  steam  jet  having  a  total 
sectional  area  of  y1^  of  a  square  inch, 
pressure  45  Ibs.,  in  3  minutes  reduced 
the  pressure  of  air  in  a  vessel  of  225 
cubic  feet  capacity  to  15  inches  of  mer- 
cury. 

Jets  can  be  arranged  for  exhausting 

or  suction  and  for  induction,  or  both.  If  we  take  two  cones,  as  in  Fig.  118,  we  shall 
find  that  there  will  be  no  suction  produced  by  the  steam  jet,  and  it  will  not  lift  the  water 
up  into  the  water  cone  ;  for  the  orifice  B  is  smaller  than  A.  And  hence  as  the  velocity 
at  A  will  be  less  than  at  B,  and  as  the  pressures  are  inversely  as  the  velocities,  there  will 
be  a  pressure  in  A  driving-  back  the  water. 

Now,  to  get  a  greater  velocity  at  A  than  that  at  B,  we  must  expand  the  nozzle 
instead  of  contracting-  it  as  shown  in  Fig.  119.     In  this  arrangement  the  steam  from  A 


FIG.  117. — Siemens'  Air  Exhauster. 


FIG.  118.— Non-lifting  Jet. 


FIG.  119. — Lifting- Jet. 


will  immediately  induce  the  air  to  follow  it  out  of  the  expanding  cone,  and  a  vacuum 
will  rapidly  be  formed  in  the  water  pipe  raising  the  water. 

Hence  we  have  two  distinct  combinations  of  cones.  In  Fig.  118  the  water  must  be 
high  enough  to  flow  in  itself,  the  jet  will  then  force  the  water  up  to  a  high  height  or 
against  a  high  pressure. 

In  the  second  combination  the  steam  jet  will  induce  a  current  of  air  at  first,  and, 
causing  a  partial  vacuum,  will  lift  the  water  and  force  it  through  B,  but  not  to  the  same 
height  or  against  the  same  pressure  as  Fig.  1 18  ;  for  the  velocity  of  the  water  is  reduced 
by  widening  the  throat  at  C  in  order  to  get  the  highest  velocity  at  A. 


96 


Modern   Engines 


Whether  the  water  enters  under  a  head  or  is  lifted  up  into  a  cone,  the  next  effect 
we  have  to  notice  is,  that  the  steam  jet  imparts  an  enormous  velocity  to  the  water, 
driving  it  from  the  second  cone  by  pressure  or  impact,  or  both.  There  is  no  doubt 
about  its  being  impulse  from  the  steam  jet  upon  the  water  which  actuates  the  water  jet, 
for  steam  at  atmospheric  pressure  will  deliver  water  against  70  Ibs.  above  atmospheric 
pressure. 

For  instance,  an  exhaust  steam  injector,  size  No.  6,  will  deliver  100  Ibs.  of  water  per 
minute  at  70  Ibs.  pressure,  using  in  that  time  8  Ibs.  of  steam  at  atmospheric  pressure. 
As  225  cubic  feet  of  steam  are  required  per  minute  to  feed  in  6000  Ibs.  of  water  per  hour, 
a  cubic  foot  at  atmospheric  pressure  steam  weighs  .039  Ib.  The  height  of  a  water 
column  of  70  Ibs.  pressure  would  be  163  feet,  and  the  velocity  of  water  8  \/i6o  =  8x  12.8 
=  say,  100  feet  per  second.  The  velocity  imparted  to  the  water  must  be  more  than  this 
by  the  amount  required  to  overcome  friction,  etc. 

The  size  of  the  delivery  is  about  £  inch  diameter,  or  .05  square  inch  ;  the  weight 
of  water  to  be  delivered  100  Ibs.,  or  1.6  Ibs.  per  second.  The  kinetic  energy  would 

"V^   If)          T  OO      X    I    6 

be  = =  — —  =  257  foot-lbs.  per  second  in  the  moving  jet ;  but  the  whole  work 

2S          64-4 

done  is  the  forcing  of  the  r.6  Ibs.  against  a  head  of  pressure  equal  to  the  height  of  a 
water  column  exerting  the  pressure  of  the  boiler,  multiplied  by  1.6,  and  added  to  the 
above.  We  can  see  that  the  first  quantity  is  work  done  on  the  water  to  start  it  into 
80  feet  motion  per  second,  from  a  state  of  rest ;  and  the  second  quantity  is  work  done 
to  carry  the  water  the  height. 


TABLE   IX. 


Pressure  of  Steam. 

Size  of 
Injector  in 

10  Ibs.      30  Ibs. 

60  Ibs. 

80  Ibs. 

100  Ibs. 

1  20  Ibs. 

140  Ibs. 

Millimetres. 

Delivery  in  Gallons  per  Hour. 

2 

25 

43 

61 

7i 

80 

87 

93 

3 

56 

97 

138 

1  60 

178 

196 

211 

4 

IOO 

173 

246 

285 

3J7 

348 

376 

5 

'57 

272 

385 

445 

496 

545 

587 

6 

226 

392 

555 

640 

715 

783 

846 

7 

307 

533 

755 

871 

973 

1067 

IIS2 

8 

402 

696 

985 

"37 

1272 

1393 

I5°5 

9 

•508 

882 

1247 

1440 

1610 

1763 

19°5 

10 

628 

1088 

1540 

1777 

1987 

2177 

2352 

1  1 

760 

1317 

1863 

2150 

2405 

2633 

2846 

12 

905 

1567 

2217 

2560 

2861 

3136 

3387 

13 

1061 

1840 

2602 

3°°5 

3358 

3680 

3975 

14 

1231 

2133 

3018 

3485 

3895 

4267 

4610 

15 

Hi3 

2450 

3465 

4000 

447i 

4900 

5292 

16 

1608 

2787 

3942 

455  J 

5087 

5575 

6022 

17 

1817 

3146 

445° 

5138 

5743 

6291 

6798 

18 

2036 

3527 

499° 

5760 

6438 

7°55 

7633 

'9 

2268 

393° 

55°° 

6418 

7i75 

7871 

8492 

20 

2513 

4355 

6160 

7110 

7950 

8710 

9410 

A  live  steam  injector  delivers  about  same  quantity  with  same  size  injector — 0.25 
inch  diameter  delivery  cone  =  0.05  square  inch  the  quantity  of  steam  would  be  Q  =  AD  x  370 
=  Ibs.  per  minute,  wherein  Q  is  the  quantity  per  minute,  A  the  area,  and  D  weight  of 
steam  per  cubic  foot  at  80  Ibs.  pressure,  370  a  constant.  D  at  80  Ibs.  pressure  =  0.1 8. 

Hence  Q  =  370x0.05  x  0.18  =  3. 33  Ibs.  per  minute,  or  ^3J  =  . 055   Ib.   per  second  to 

60 


Injectors  97 


lift  1.7  Ib.  of  water  against  80  Ibs.  pressure.     A  better  efficiency  than  for  exhaust  steam, 
from  the  point  of  view,  as  a  water  jet  producer. 

We  have  seen  that  the  impulse  of  a  steam  jet  is  at  the  throat  of  a  nozzle    -2 — —  ; 

2g 
a  jet  like  that  would,  if  all  its  impulse  were  absorbed,  give  20  horse-power. 

3.33  Ibs.  of  steam  per  minute  would  give  10  horse-power  in  a  steam  engine  ;  in  this 
injector  it  lifts  100  Ibs.  185  feet  in  a  minute,  or  18,500  foot-lbs. — a  little  more  than 
i  horse-power  of  work  done.  It  is  clear,  then,  that  although  "the  impulse  before  impact 
must  be  the  same  as  after  impact "  may  be  true,  that  very  little  of  it  is  communicated  to 
the  water  as  impulse  energy. 

The  fundamental  equation  is — 

W=i28oxD2x/P~;  or 

w=i.98^2v/p; 

where  W  =  water  weight  to  be  injected  per  hour. 
P   =  pressure  in  Ibs. 
D  =  diameter  of  throat  in  inches. 
d    =  millimetres. 


SIZES  OF  JETS 

In  approximate  calculations  for  construction,  if  W  =  lbs.  of  feed  water  supplied  per 
Ib.  of  steam,  then  W  +  i  will  be  the  quantity  entering  the  boiler. 

The  total  heat  of  i  Ib.  of  steam  reckoned  from  zero  Fahr.  =  h^  x^  Lr 

{wherein  h^  =  sensible  heat  at  the  steam. 
A:1  =  dryness  fraction. 
Lj  =  latent  heat  at  the  given  pressure. 

When  the  quantities  are  combined  the  total  heat  in  the  combining  cone  =  ^3,  the 
heat  in  the  feed  water  =  hy 

The  heat  given  up  in  condensation  of  the  steam  =  h^  +  xL^  —  h^  thermal  units,  and 

the  heat  gained  by  the  feed  water  =  W(A3  —  h^  units.     W  will  therefore  =  — *   l — ?. 

h^-h^ 

For  the  velocity  of  the  steam  at  the  throat  of  the  steam  orifice  we  have  an  equation 
already,  and  may  be  taken  as  nearly  constant  at  1500  per  second. 
V3,  the  velocity  of  the  combined  steam  and  water  in  the  delivery 


according  as  the  feed  water  is  above  or  below  the  delivery.     If  it  is  on  a  level  with  the 

•\7 

delivery,  V3  = 


If  W2  =  the  total  water  in  Ibs.  per  hour  to  be  fed,  the  weight  per  second  will  be 

W  W 

,  and  the  volume  — — |—  x  volume  of  i  Ib.  of  steam  at  the  pressure  given  in  the 


3600  W'  3600  W 

steam  orifice  =  V9 ;  therefore    „  2    2  =  total  volume. 

3600  W 

The   volume  of  steam  passing  the  steam  nozzle  is  AV2  cubic  feet,  if  A  is  given 

W  V 

in  square  feet.     V2  we  have  taken  as  1500.     A2V2=   ,-Jl^'     Taking  the  value  of  V2  as 

/  W  V 

assumed,  and  irr<?  for  A2,  we  find  that  r2  =  the  steam  nozzle  =  o.  1 1 3  ^/  w  v  •    The  com- 

2 
/  T  —  WW 

bining  cone  orifice  =  rz  =  o.  1 13^  2. 

v       W2rV3 

An  example  may  be  taken  for  500  horse-power,  boiler  feed  10,000  Ibs.  of  water 
VOL.  i. — 7 


Modern   Engines 


required  per  hour  =  W2  ;  feed  water  at  60°  Fahr.  feed  water  on  the  level,  temperature  of 
feed  170°,  absolute  steam  pressure  100  Ibs. 

The  quantity  of  feed  per  Ib.  of  steam  calculates  out  at  8.82  Ibs.   (in  practice  it 

is  nearer  7).     W  =  by  equation  =  2^  '  9  n  -  3~  *3  '3$  =8.82.      Velocity  of  delivery  is 


-^  -  — 

.  o2  X  1500 


=0.26  =  .  52 


9.82  x  io,ooo 
$.82  x  62.5  x  150 


=  0.122, 


found  by  V3  =  -—  -—  152.     Radius  of  steam  orifice,  1  =  O 

Q.O2 

inch  diameter  =  0.235  square  inch. 

For  the  radius  of  the  combining-  cone  orifice,  *2  =  OtI 

or  0.244  inch  diameter. 

These  are  the  fundamental  dimensions  from  which  the  design  can  be  completed. 
The  exhaust  steam  injector  acts  upon  the  same  principles.     The  maximum  flow  of 
steam,  we  have  already  seen,  occurs  when  p-pi  is   less  than  -f  of  p   boiler  pressure 

and  />!  the  pressure  blown  into.  Now,  if  we  take  exhaust 
steam  at  15  Ibs.  above  zero,  and  assume  that  the  pressure 
falls  to  8  Ibs.  in  the  combining  cone,  we  would  obtain  the 
maximum  weight  flow  of  steam,  for  T8r  is  less  than  f  . 

The  volume  of  the  steam  per  cubic  foot  is  large,  and  so 
we  must  make  the  steam  cone  A  larger  in  proportion,  for  it 
still  takes  i  Ib.  of  steam  to  raise  up  7  Ibs.  of  water.  0.038 
is  the  weight  of  i  cubic  foot  at  atmospheric  pressure  ;  at 
100  Ibs.  pressure  in  the  example  quoted  the  weight  is  0.23, 
so  that  to  admit  the  same  quantity  of  steam  the  orifice  areas 
A  should  be  as  the  weights  .23  is  to  0.038,  about  6  to  i 
=  6  x  .235  =  1.41  square  inch.  The  water  must  have  a  slight 
fall  into  the  injector. 

Practically  i  Ib.  of  steam  raises  7  Ibs.  of  water,  and  the 
steam  cone  would  be  7  to  i  against  a  steam  cone  at  100  Ibs. 
pressure;  hence  weight  of  steam  Q  —  AD  370=  1.635  square 
inch  x  0.038  x  370  =  22.25  Ibs.  of  steam  per  minute  delivered, 
or  1335  Ibs.  per  hour,  and  1335x6  =  9345  —  very  little  less 
than  the  10,000  delivered  by  the  live  steam.  Where  there 
are  non-condensing  engines  exhaust  steam  can  be  used  with 
advantage  to  raise  large  volumes  of  water. 

The  sensible  heat  of  the  exhaust  steam  plus  the  latent 

heat  as  it  enters  the  steam  cone  is  1147,  and  that  of  the  steam  at  100  Ibs.  =  1171 
per  Ib.,  so  that  if  we  take  1.022  Ibs.  of  exhaust  steam  it  will  deliver  the  same 
heat  in  the  combining  cone  as  i  Ib.  at  100  Ibs.  pressure,  so  that  the  fact  that  the 
exhaust  steam  will  feed  against  80  Ibs.  pressure,  lifting  7  times  its  own  weight,  is  not 
so  mysterious. 

We  come  now  to  examine  a  few  typical  injectors.  For  locomotive  feeding  they  are 
incomparable.  There  is  no  lift  in  this  case,  and  steam  pressure  need  not  vary  much,  so 
that  a  simple  injector  meets  with  great  favour.  Fig.  120  shows  it  in  its  simplest  form. 
A  is  the  steam  cone,  B  the  steam  orifice,  C  the  combining  cone.  in  which  the  steam  is 
seen  as  a  cone  wedging  itself  into  the  water,  condensing  and  flowing  across  an  air  space 
D  into  the  delivery  cone  E. 

The  air  space  D  is  of  importance,  as  it  provides  a  relief  from  back  pressure  which 
would  arise  if  from  any  cause  the  quantity  flowing  at  d  could  not  get  freely  away  though  e. 
The  flow  of  fluid  must  be  unchecked,  so  as  to  maintain  the  velocity.  Hence  if  a  surplus 
of  fluid  were  to  flow  and  no  opening  D  provided,  the  velocity  would  be  checked.  By 
providing  an  overflow  any  surplus  is  shaved  off  and  escapes,  so  that  no  obstacle  is 
presented  to  the  full  velocity  from  the  combining  cone. 


FIG.  1 20. — Loco  Injector. 


Injectors 


99 


In  discussing  cones  and  water  lifting-,  we  have  shown  in  Figs.  1 18  and  1 19  that  the 
combining  cone  outlet  must  be  larger  in  area  than  the  steam  cone  orifice,  in  order  to  start 
the  injector  on  a  lift  of  water.  Sellars  was  the  first  to  patent  a  device  for  this  purpose, 
shown  in  diagram  Fig.  121.  He  fits  for  this  purpose  a  steam  tight  rod  with  a  small  nozzle 
drilled  in  its  end  marked  the  lifter.  This  nozzle  slides  by  a  screw  in  the  steam  cone,  and 
gets  its  steam  from  holes  drilled  obliquely  into  the  nozzle  from  the  side  of  the  rod  in  the 
position  shown.  It  closes  the  main  steam  cone 
and  delivers  a  small  jet  to  lift  the  water  and  start 
with.  When  started  the  little  nozzle  is  withdrawn 
by  the  screw,  and  its  steam  parts  closed. 

A  better  method  was  introduced  by  Davis 
and  Metcalfe  in  the  flap  nozzle  injector  (Fig.  122), 
wherein  the  nozzle  is  split  and  hinged  so  that 
when  steam  is  turned  on  it  opens  up  and  presents 
an  orifice  greater  than  the  steam  cone,  and  so 
forms  the  vacuum  to  lift  the  water  for  starting. 
When  the  water  arrives  it  is  driven  down  in  a 
contracting  stream,  and  the  flap  closes  upon  it  as 
a  partial  vacuum  is  formed  around  the  stream  of 
water.  It  is  thus  automatic,  and  if  from  any 
cause  the  injector  should  stop  it  will  restart  again.  This  instrument  is  well  adapted 
for  locomotives,  as  it  requires  no  attention  to  keep  it  at  work. 

This  restarting  arrangement  is  also  employed  in  the  same  makers'  exhaust  steam 
injector  shown  in  Fig.  123,  so  that  it  starts  off  itself  every  time  the  engine  is  stopped 
and  started.  This  injector  is  very  simple  and  effective  and  easily  adjusted.  By  turning 
the  nut  at  the  bottom  the  combining  cone  can  be  raised  or  lowered  so  as  to  nicely  adjust 

EXHAUST   STEAM 


FIG.  121. — Lifting-  Nozzles. 


FlG.  122. — Self-starting 
Jet. 


REGULATOR  - 


FIG.  123. — Exhaust  Steam 
Injector. 


FlG.  124. — Automatic  Restarting 
Injector. 


the  water  supply.  The  conical  rod  in  the  steam  cone  causes  the  steam  jet  to  enter  as  an 
annular  jet,  and  so  concentrates  it  upon  the  annular  water  jet.  The  steam  in  the  centre 
of  a  solid  steam  jet  not  being  so  effective  as  that  on  its  outer  periphery,  the  division  in 
the  overflow  is  meant  for  a  water  seal  to  prevent  inlet  of  air. 

Another  method  for  automatic  restarting  is  shown  in  the  latest  Penberthy  injector, 
Fig.  124.  Although  introduced  by  Mr.  R.  G.  Brooke,  we  select  the  Penberthy  as 
showing  also  the  diverging  steam  cone,  which  must,  as  in  the  De  Laval  cone,  increase 


IOO 


Modern   Engines 


the  impulse.  The  combining-  nozzle  is  nearly  parallel,  and  cut  into  two  lengths.  In 
order  to  restart  automatically,  a  flap  valve  A  opens  or  closes  a  chamber  around  the 
division  of  the  cone  to  the  overflow  O,  and  this  valve  opens  and  closes  automatically. 

The  ordinary  overflow  is  also  used  at  the  narrow  throat  of 
the  delivery  cone. 

There  are  many  other  designs  for  restarting  auto- 
matically, all  based  on  this  principle  of  an  automatic  valve 
opening  by  the  pressure  to  allow  of  the  steam  blowing  out 
the  air  and  the  water  to  follow  it.  Immediately  condensation 
occurs  on  arrival  of  the  water,  the  valve  closes  by  a  partial 
vacuum  forming. 

The  original  injector,  the  Giffard,  had  a  tapered  rod  to 
regulate  the  steam,  and  a  moving  cone  to  regulate  the 
water.  Wherever  injectors  have  to  work  under  different 
conditions  of  water  and  steam  supply  it  is  desirable  to 
have  regulation  of  this  kind.  The  original  Giffard  in- 
jector is  shown  in  Fig.  125.  The  steam  cone  slides  by 
means  of  the  side  screw,  and  the  tapered  rod  by  means 
of  the  central  screw  and 
hand  wheel.  By  moving 
either  or  both,  adjustment 
can  be  made  for  a  large 
variety  of  different  condi- 
tions. In  fact,  it  is  an  ex- 
cellent machine  with  which 
to  give  or  get  an  object 
lesson  on  the  effects  of 
varying  pressures,  tempera- 
tures, and  lifts.  It  is,  how- 
ever, not  restarting  auto- 
matically. 

Mr.  Brookes'  automatic  restarter,  fitted  with  a 
sliding  cone,  which  by  moving  the  handle  adjusts 
both  steam  and  water  simultaneously,  is  shown  in 
Fig.  126.  The  combining  cone  is  divided  and  fitted 
with  a  closing  and  opening  automatic  valve  to  the 
overflow.  To  make  it  restart,  it  has  also  the  ordin- 
ary air  space  overflow.  The  steam  cone  is  carried 
on  a  piston  working  in  a  cylinder,  and  can  be  screwed 
out  or  in  by  the  quick  thread  screw.  A  conical  end  FIG.  126.— Adjustable  Injector, 
on  the  screw  regulates  the  steam  inlet,  and  the 

movement  of  the  outlet  orifice  regulates  the  water,  decreasing  the  one  at  the  same 
time  that  the  other  increases.  Hence  a  position  can  be  found  for  satisfactory  working 
over  a  long  range  of  varying  conditions. 


FIG.  125. — Giffard  Injector. 


COMPOUND   INJECTORS 

With  a  single  injector  the  temperature  of  the  feed  cannot  exceed  200°  Fahr., 
because  of  the  low  pressures  in  the  cones.  Any  higher  temperature  generates  steam 
and  destroys  the  action  ;  but  if,  with  one  injector,  we  force  feed  water  into  another, 
we  can,  on  account  of  the  higher  pressures,  feed  into  the  boiler  at  much  higher 
temperatures. 

We   will   illustrate   one   by   Green   &    Boulding,    of   London,    called    the    Buffalo 


Ejectors 


101 


Injector,    as    a    very   well    designed    example.      The    first   injector  on   the   right-hand 

side  is  designed  to  lift  the  water  and  force  it  into   the   high   pressure   injector.      On 

lifting  the  handle  13  (Fig.  128),  spindle  2  lifts  the  steam  valve  through  21  and  allows 

STE»M  steam  to  flow  through  steam  cones  24  and 

22.  The  lifting  injector  draws  water  through 
21  and  forces  it  through  combining  and 
delivery  cone  23,  whence  it  enters  combin- 


EXHAUST     STEAM 


FIG.  127. — Compound  Injector  FIG.  128. — Section  of  Compound  Injector. 

ing  cone  25,  and  from  thence  to  the  boiler.  The  overflow  valve  of  the  forcer  is  worked 
by  spindle  17  by  the  side  rod  shown  in  elevation  (Fig.  127),  which  allows  it  to  close 
when  the  machine  is  at  work,  and  opens  it  when  stopped.  When  the  water  arrives  and 
steam  condenses  a  water  pressure  is  produced  in  discharge  of  the  forcer  25,  which 

closes  the  overflow  valve.    This  automatic  clos- 
ing of  the  valve  is  the  feature  of  this  injector. 

Exhaust  injectors  can  be  combined  with  live 
steam  injectors  to  feed  into 
very  high  pressures.  Messrs. 
Holden  &  Brookes'  excellent 
arrangement  is  shown  in  Fig. 
129.  A  jet  of  live  steam  starts 
the  exhaust  injector  through 
pipe  A,  and  it  delivers  at  first 
partly  through  P  and  the  live 
steam  injector.  When  fully 
started,  all  the  feed  takes 
place  through  the  live  steam 
injector. 

AIR  EJECTORS 

We  have  already  referred 
to  these.  For  some  purposes 
they  are  admissible,  such  as 
on  a  locomotive,  where  a  fan 
or  pump  would  be  objection- 
able on  account  of  requiring  attention.  They  are  not  economical. 
The  only  case  of  steam  jets  being  employed  with  economy  in  prime 
movers  is  that  of  the  De  Laval  turbine,  where  it  is  utilised  by  special  means. 

One  application,  however,  deserves  notice,  that  of  furnace  blowers  where  steam 
is  plentiful  and  cheap,  as  it  is  where  the  waste  heat  generates  it.  Messrs.  Korting 
Brothers  supply  a  blower  as  shown  in  Fig.  130.  On  the  bi-conical  pipe  is  fixed  a  head 


FIG.  129. — Compound  Injector. 


FIG.  130. — Air 
Ejector. 


102 


Modern   Engines 


containing-  three  or  four  cones,  the  one  blowing-  into  the  other  ;  and  the  top  one  a  small 
steam  cone.  The  object  for  using-  a  number  of  cones  in  succession,  each  succeeding 
cone  increasing-  in  size,  is  to  induce  a  large  volume  of  air  at  low  pressure.  The  steam 
sets  up  a  flow  in  the  first  jet,  this  induces  an  additional  flow  in  the  next,  and  so  on  until 
the  accumulated  blast  enters  the  large  delivery  pipe. 

W  Ibs.  of  air  are  set  in  motion  by  i  Ib.  of  steam  with  a  velocity  V  of  steam  and 
a  velocity  Vl  of  the  mixture,  and  the  velocity  of  the  air  as  it  enters  the  cone  by  suction 

v+wv  v2 

V,,  then  the  momentum  is  M  =  - ^rr^-     The  head  of  steam  is  — ,  and  of  the  combined 

1+ W  2g 

V  2 
air  and  steam    -!-.     The  efficiency  is  difficult  to  determine  accurately ;  theoretically,  it 


should  be  — It  therefore  increases  with  the  velocity  of  the  air   entering 

each  jet.     Hence  increasing  the  velocity  from  one  to  the  other  in  succession  is  a  gain. 


EJECTOR  CONDENSER 

These  machines  are  designed  to  condense  the  exhaust  steam  from  engines  to  form  a 

working  vacuum.  They  have  the  drawback  of  the  jet 
condensers  and  others  in  mixing  the  condensed  steam 
water  with  the  condensing  water.  And  therefore  the  pure 
condensed  water  is  mixed  with  salt  or  impure  water ; 
whereas,  in  the  surface  condenser,  canal,  river,  or  sea 
water  may  be  used  for  condensing,  while  the  pure  con- 
densed water  of  the  exhaust  may  be  saved  for  boiler  feed- 
ing. However,  they  have  a  large  field  of  usefulness  where 
these  considerations  do  not  apply  with  any  force. 

This  invention  is  due  to  Mr.  Alexander  Morton  of 
Messrs.  Morton  &  Thomson,  Glasgow.  In  this  condenser 
the  proportion  of  water  to  steam  required  is  much  the 
same  as  in  surface  or  jet  condensers,  about  27  Ibs.  of  water 
to  i  of  steam. 

Morton,  scientifically  from  the  first,  designed  his 
ejectors  to  make  use  of  the  smallest  head  of  condensing 
water, — in  fact,  it  could  be  submerged  in  a  river  or  pond 
of  cold  water  and  so  draw  in  the  condensing  water.  He 
designed  them  to  lift  the  condensing  water  by  means  of  a 
small  supplementary  live  steam  jet ;  also  to  regulate  the 
water  supply  cones  by  movable  cones  ;  also  a  special 
automatic  regulator  to  regulate  the  water  supply.  All 
these  devices,  however  ingenious  and  in  some  few  cases 
necessary,  introduced  the  elements  of  complication,  and 
attention  was  required  for  them. 

In  practice  it  is  found  better  to  provide  an  ejector  condenser  of  sufficient  water 
capacity  for  the  maximum  load,  and  a  fair  vacuum  ;  and  to  maintain  a  head  of  at  least 
15  feet  on  the  condensing  water,  if  not  by  a  natural  fall,  then  by  a  centrifugal  pump 
driven  by  power.  For  wherever  there  is  an  ejector  condenser  there  will  be  power 
available. 

With  a  fall  of  16  feet  the  velocity  of  the  water  =  8\/ 16  =  32  feet  per  second.  Hence 
it  will  balance  the  atmospheric  pressure  and  produce  a  vacuum  without  the  action  of  the 
exhaust,  and  maintain  a  good  vacuum  under  all  ordinary  conditions.  It  is  therefore 
usual  now  to  employ  a  plain  condenser,  and  in  all  cases  provide  a  fall  of  condensing 


FIG.  131. — Morton's  Simple 
Condenser. 


Ejectors 


103 


water  usually  by  pump.  Morton's  plain,  simple  fixed  capacity  condenser  is  shown  in 
diagram  Fig.  131.  The  water  enters  the  cone  B  flowing  out  at  A  at  about  32  feet  per 
second,  forming  a  rod  of  cold  water.  Rushing  at  this  velocity,  the  exhaust  enters  at 
D,  and  surrounds  this  cold  rod  of  water  ;  it  quickly  condenses  thereon,  increasing  its 
diameter  slightly,  and  is  carried  with  the  rod  right  into  G  the  delivery,  from  which 
it  cannot  return,  for  the  pressure  due  to  the  velocity  is  greater  than  an  atmosphere. 
Any  air  in  the  steam,  if  not  of  more  than  usual  quantities  in  exhaust 
steam,  is  also  carried  down. 

The  Korting  form  of  this  ejector  provides  a  longer  contact 
for  the  steam  and  water,  by  using  a  long  series  of  cones  as  shown 
in  Fig.  132.  I  have  used  this  condenser  with  great  success  in  many 
cases,  in  nearly  all  of  which  the  condensing  water  has  been  pumped 
up  by  centrifugals.  For  each  Ib.  of  steam  we  allow  27  Ibs.  of  water 
lifted  16  feet,  and  allowing  25  Ibs.  of  steam  per  horse-power.  Thus 
we  get  the  power  required  at  the  pump  =  25  x  27  =  condensing  water 
per  horse-power  =  675  Ibs. ;  and  675  x  16  =  foot-lbs.  =  10,800  per  hour, 
or  1 80  foot-lbs.  per  minute  per  horse-power.  As  the  friction  and 
other  losses  amount  to  nearly  as  much,  it  is  safe  to  calculate  on  360 
foot-lbs.  per  minute  per  horse-power,  or  roughly  about  i  per  cent,  of 
the  engine  power. 

A  good  vacuum  increases  the  power  of  steam  turbines  very 
largely,  so  that  it  is  good  economy  even  to  provide  an  artificial  head 
and  cooling  apparatus  for  condensing  water ;  in  which  case  a  simple 
ejector  condenser  is  by  far  preferable  to  any  other. 

A  water  pressure  intensifier  by  means  of  a  water  jet  has  been 
used  to  increase  the  head  of  water  in  town  supply  pipes,  in  case  of 
a  fire  requiring  a  jet  beyond  the  reach  of  the  ordinary  head.  This 
practice  is,  however,  only  possible  where  a  high  pressure  supply  FIG.  132.— Korting- 
exists  alongside  of  the  ordinary  supply.  The  jet  is  shown  in  Ejector  Conden- 
Figf.  133.  sen 

In  London,  Glasgow,  and  other  large  towns  a  hydraulic  pressure  supply  at  750  Ibs. 
is  laid  on  for  working  lifts  and  high  pressure  rams  and  presses.  This  supply  can  be  led 
into  an  ordinary  supply  pipe  A  in  a  very  fine  jet,  as  shown  in  E,  and  the  flow  of 
water  accelerated,  and  the  pressure  increased  in  the  fire  extinguishing  jets.  It  requires 
care  in  using  the  jet.  The  delivery  jets  must  all  be  freely  opened  before  the  high  pressure 
jet  is  opened,  and  they  must  not  be  closed  before  the  high  pressure  jet  is  shut  off. 

In  Fig.  134  we  give  a  section 
of  the  Penberthy  No.  2  water  jet 
lifter,  showing  the  expanding  steam 
nozzle.  They  are  convenient  in  some 
cases  for  emergency  and  tempor- 
ary use ;  but  all  water  lifters  by 
steam  jets  are  wasteful  of  steam, 
and  therefore  are  not  adopted  for 
regular  pumping  of  water  to  higher 
levels. 

We  shall  conclude  our  examination  of  fluid-upon-fluid  engines  and  machines  by  a 
briet  reference  to  ship  propulsion  by  fluid  or  jets,  a  method  which  is  worthy  of  con- 
sideration along  with  the  only  alternative,  the  screw  propeller  ;  which,  in  fact,  is  only 
a  pump  outside  the  vessel  producing  a  water  stream,  the  reaction  of  which  propels  the 
boat. 

The  propulsion  ot  steam  vessels  by  water  jets  occupied  the  attention  of  the  British 
Government's  Admiralty  some  thirty  years  ago.  They  were  tried  on  a  vessel  called  the 


FIG.  133. — Water  Pressure  Intensifier  Jet. 


104  Modern  Engines 


Waterwitch  with  some  success,  but  the  experiments  for  some  reason  or  other  were  not 
concluded,  and  no  report  ever  issued  of  results. 

Mr.  J.  R.  Ruthven  gave  a  brief  report,  which  was  read  before  the  Society 
of  Engineers  and  Shipbuilders,  Glasgow,  27th  October  1891,  from  which  we 
gather  : — 

The  experimental  trials  made  were  those  of  the  Waterwitch,  a  gunboat  built  for 
the  Admiralty,  with  the  purpose  of  comparing  the  propelling  and  manoeuvring  power  of 
the  jet  with  the  screw.  For  this  purpose  two  screw  ships,  the  Viper  and  Vixen,  twin 
screw  vessels  of  about  the  same  tonnage  and  same  midship  section,  were  built  as  fair 
competitors  with  the  jet  propelled  Waterwitch. 

The  water  jets  are  obtained  by  a  centrifugal  pump  which  takes  its  supply  from  the 
sea,  or,  in  case  of  heavy  leakage,  from  the  hold  of  the  ship.  The  centrifugal  wheel 
is  placed  horizontally  in  the  ship,  and  is  driven  direct  by  steam  engines  working 
horizontally. 

There  is  an  arrangement  to  reverse  the  direction  of  the  discharge  of  the  jets,  so 
that  the  vessel  can  be  propelled  ahead  by  discharging  the  water  astern,  or  astern  by 
discharging  ahead,  or  the  jet  at  one  side  of  the  vessel  may  discharge  ahead,  and  on  the 
other  astern  ;  in  this  case  the  ship  neither  goes  ahead  nor  astern,  but  turns  round  in  her 
own  length. 

The  twin  screw  vessels  Viper  and  Vixen  and  the  jet  propelled  Waterwitch, 
common  ships,  all  of  the  same  midship  section,  and  nearly  same  displacement.  The 
twin  screw  vessels  had  double  stern  posts  and  two  rudders  at  the  stern,  the  Waterwitch 

had  two  rudders,  one  at  the  bow  and 
one  at  the  stern,  each  working  in  a 
heavy  frame,  intended  to  be  used  as 
a  ram,  at  either  end.  This  must  have 
caused  considerable  increased  obstruc- 
tion, and  as  the  ship  is  longer,  on 
account  of  these  rudders  and  frames, 

~  more    difficult   to   turn    in    her    own 

riG.  134. — "  Penberthy     water  Jet  Lifter. 

length. 

In  1863  it  was  decided,  by  the  Admiralty,  to  test  the  water  jet  on  a  large  scale. 

Some  time  before  this  date  the  Admiralty  had  been  satisfied  on  the  feasibility  of  the 
plans,  by  themselves  making  and  applying  the  jet,  in  an  old  screw  gunboat,  the  Jackdaw, 
at  Devonport,  by  means  of  a  series  of  teeth  wheels  and  shafts,  working  from  the  old 
screw  shaft  to  the  pump,  which  had  only  one  outlet  led  to  one  side  of  the  ship.  With 
this  imperfect  arrangement  the  ship  was  propelled,  and  a  speed  was  attained  which 
satisfied  the  Admiralty  that  it  gave  promise  of  a  success. 

An  important  point  in  connection  with  the  jet  as  a  propeller  must  be  noted,  that  is, 
its  power  in  stopping  the  vessel.  This  was  tried  with  the  Waterwitch,  and  from  going 
full  speed  ahead  the  order  was  given  to  reverse  the  action  of  the  jets,  and  the  vessel  was 
stopped  in  nearly  her  own  length.  This  was  ascertained  by  throwing  a  billet  of  wood 
square  from  the  bow  on  the  order  given  to  reverse  the  jets,  and  the  ship  was  stopped 
when  the  floating  billet  was  level  with  the  stern.  This  is  a  very  remarkable  property, 
which  the  screw  cannot  approach. 

This  power  of  quickly  stopping  and  reversing  a  ship's  headway  must  be  of  great 
importance  to  the  safety  of  the  ship,  by  enabling  her  in  many  cases  to  avoid  collisions 
which  the  continual  increase  of  speeds  makes  more  and  more  dangerous.  In  passing,  it 
may  be  remarked  that  the  great  stopping  power  is  a  proof  of  the  efficiency  of  the  water 
jet  as  a  propeller,  the  value  of  which  is  obvious  in  quickly  stopping  and  backing,  while 
with  the  great  power  of  turning  there  is  no  danger  from  loss  of  steerage  way,  as  the 
ship  can  be  effectually  steered  by  the  jets  when  she  has  little  or  no  way  on  her,  at  which 
time,  of  course,  the  rudder  is  of  little  or  no  use. 


Jet  Propellers 


I05 


TABLE   X. 


Vessel's  name 

Vixen 

Viper 

Waterwitch 

Nominal  horse-power  . 

160 

160 

160 

Date  of  trial 

2nd  Aug.  1867 
Ft.  In. 

5th  Aug.  1867 
Ft.  In. 

nth  Oct.  1867 
Ft.  In. 

9-ioth  Aug.  '67 
Ft.  In. 

28th  Aug.  1867 
Ft.  In. 

3rd  Sept.  1867 
Ft.  In. 

1  2th  Oct.  1867 
Ft.  In. 

Draught  -j   .  °.5e  "        ' 

9  10 
ii  ii 

9  ii 

II    IO 

9  ii 

II    10 

IO 

II 

9 
8 

10    7J 
n     ij 

9     9 
n     9 

10     7 

II       2 

Midship  Section,  square  feet 

336 

335-7 

336 

347 

336 

333 

336 

Boiler  power 

Full 

Half 

Full 

Half 

Full 

Half 

Full 

Half 

Full   i   Half 

Full 

Half 

Full 

Half 

Revolutions 

108.6 

85-1 

109.2 

82 

110.5 

83-7 

40.7 

26.2 

4i-5 

28.2 

40.9 

27.9 

40.4 

30.6 

Indicated  horse-power.        . 

657 

336 

652 

334 

696 

344 

777 

226 

801 

271 

769 

268 

759 

348.5 

Speed,  knots 
Speed  8  x  Midship  Section 

9.06 
379-9 

7-347 

395 

9-475 
438.5 

7-334 

9-586 
435-4 

7.625 
431-3 

9-237 
351-9 

6.227 
369.6 

9.219 

328.7 

6.047 

273-9 

8.88 
303-3 

6.326 
3I4-3 

9.299 
357-8 

7.206 
359-6 

I.H.P. 

In  the  discussion  upon  this  paper  it  is  interesting  to  hear  what  her  commander  said 
about  her. 

Captain  Sharpe,  R.N.,  said:  "  I  can  safely  say,  having  commanded  the  Waterwitch 
during  the  time  the  experiments  took  place,  I  always  urged  (and  still  think)  that  they 
were  never  carried  on  to  the  extent  that  they  might  have  been.  Whilst  in  command 
of  the  Watervoitch  I  felt  the  extreme  advantage  of  having  her  always  under  my  own 
individual  command.  I  could  stop  her,  go  astern,  turn  the  ship,  or  do  anything  without 
reference  to  the  engineers.  The  only  thing  I  have  to  add  is  that  during  the  time  I  was 
in  the  ship  I  was  very  sorry  to  think  that  so  little  use  came  of  it,  and  that  so  little  has 
since  been  done." 

The  subject  has  dropped,  although  there  are  some  small  steamers  of  the  lifeboat 
class  still  made  with  jet  propellers,  and  the  introduction  of  high  speed  turbines  has 
proven  that  there  are  difficulties  with  propellers  of  the  screw  type  ;  hence  jets  may  after 
all  be  reverted  to.  It  will  therefore  be  of  interest  to  investigate  the  matter  a  little 
further,  with  thirty  years'  more  experience  and  progress  than  Mr.  Ruthven  had  to  aid 
him. 

The  late  Mr.  Miller,  secretary  of  the  Society  of  Engineers  and  Shipbuilders,  Glasgow, 
also  read  a  paper  on  jet  propellers.  His  proposal  was  not  made  as  a  serious  attempt  at 
ship  propulsion  in  general,  but  with  a  view  to  assist  in  the  case  of  a  failure  of  the  screw, 
its  shaft,  or  engines.  So  long  as  the  boilers  were  intact  he  calculated  that  a  steam  jet, 
delivering  astern  all  the  steam  the  boilers  could  make,  would  propel  her  by  reaction  at 
3  knots  an  hour,  a  speed  not  much  but  better  than  nothing  at  all.  The  difficulty,  however, 
arises,  that  if  far  from  land  she  would  burn  up  all  the  fuel  long  before  getting  to  port, 
and  therefore  never  could  finish  the  voyage.  If  she  had  coal  for  12  days  at  12  knots 
steaming,  she  could  not  travel  far  at  3  knots  on  the  coal  in  stock. 

The  screw  propeller  is  a  pump  outside  of  the  vessel,  which  thrusts  the  water  away, 
and  the  reaction  propels  the  ship.  The  jet  propeller  driven  by  a  pump  does  the  same 
thing  exactly.  The  only  difference  is,  the  pump  is  inside  in  one  case,  and  outside  in  the 
other. 

With  the  outside  pump  there  are  many  difficulties,  well  known.  The  loss  of  the 
propeller  is  not  uncommon,  neither  is  the  shaft  breaking  uncommon.  And  as  the  screw 
is  necessarily  a  slow  speed  pump,  the  shaft  has  become  of  enormous  weight  and  diameter. 
With  the  inside  pump  and  propeller  jets  high  speed  pumps  can  be  used.  There  are  no 
propellers  or  shafts  liable  to  be  lost  or  broken.  With  obvious  advantages  it,  however, 
has  some  natural  limits  which  may  keep  it  from  extensive  adoption. 

It  is  all  a  question  of  velocities  and  pressures  to  be  properly  apportioned.  For 
instance,  in  Mr.  Miller's  proposal  to  use  a  large  steam  jet,  to  get  any  efficiency,  the  ship 


106  Modern  Engines 


should  move  at  some  large  fraction  of  velocity  of  the  jet  at  the  orifice.  This  velocity  is 
about  1500  feet  per  second,  or  about  17  miles  a  minute. 

The  water  jet,  then,  as  a  very  first  requisite,  must  have  a  velocity  about  equal  to 
that  of  speed  desired,  and  this  limits  its  efficiency  and  usefulness. 

Suppose  the  speed  to  be  fixed  at  10  knots  per  hour,  it  has  been  found  that  at  5  knots 
and  upwards  the  power  required  is  as  the  square  of  the  speed  nearly  ;  for  our  present  pur- 
poses that  is  at  any  rate  assumed.  At  5  knots  it  takes  £  of  a  Ib.  pull  or  push  to  propel 
a  vessel  for  every  square  foot  of  wetted  surface,  so  that  if  we  assume  a  ship  with  6000 
square  feet  of  wetted  surface  it  will  require  1000  Ibs.  thrust  to  keep  up  5  knots.  Then  if 

io2  x  looo     100,000 
10  knots  are  required,  we  get g = =  4000  Ibs.  thrust  for  io  knots. 

O  0 

io  knots  is  a  rate  of  travel  =  60,870  feet  per  hour,  and  - •     '  -  =  nearly  16  feet   per 

second.  Now,  this  is  the  point  where  a  limit  comes  in.  This  speed,  16  feet  per 
second,  is  the  speed  of  efflux  which  the  jet  should  have  to  get  100  per  cent,  efficiency. 
We  can  calculate  the  head  or  pressure  of  water  which  will  give  this  velocity. 

V2 
H=  —  =  4  feet  head,   or  about  2  Ibs.  pressure.     Now,  if  we  divide  the  total  thrust 

2S 
required  by  this  pressure,   - —  =2000  =  the   area   of  jet   in   section   in   square   inches, 


2000 


=  13.2  square  feet.     A  pipe  of  about  50  inches  diameter  would  give  this  area. 


144 

Hence  to  get  efficiency  we  require  a  large  pump,  and  so  large  that  we  put  it  outside 
in  the  form  of  a  screw  in  screw  propellers. 

But  the  pressure  is  small,  2  Ibs.  or  4  feet  head,  so  that  although  the  velocity  of  the 
water  jet  issuing  from  the  ship  is  limited  to  this  velocity,  we  might  run  a  small  centri- 
fugal pump  at  a  high  velocity,  and  the  water  may  have  a  greater  velocity  in  the  pipes 
inside  the  ship.  13  square  feet  of  area  x  16  feet  velocity  =  13  x  16  =  208  cubic  feet  of  water 
per  second,  and  208  x  62.5  =  13,000  Ibs.  of  water  per  second,  52,000  foot-lbs.  per  second. 
Nearly  100  horse-power  would  be  required  in  the  water,  and  probably  the  efficiency 
would  be  less  than  50  per  cent.,  so  that  an  indicated  horse-power  would  be  required  of 
more  than  200  in  all. 

Now,  suppose  we  double  the  pressure  to  an  8-foot  head,  then  velocity  8  x/8~=  2.83  x 
8  =  22.64  feet  per  second  velocity.  With  double  the  pressure  we  do  with  half  the  jet 
area, — 6.5  square  feet,  or  1000  square  inches.  A  32-inch  pipe  or  jet  would  now  suffice. 

The  velocity  is  22  feet,  and  this  multiplied  by  6.5  =  cubic  feet  of  water  per  second 
=  143  cubic  feet,  9000  Ibs.  nearly.  And  energy  per  second  =  9000  x  8  =  72,000  foot-lbs. 
=  130  horse-power  in  the  water,  so  that  the  speed  of  the  vessel  would  be  still  io 
knots  ;  but  instead  of  100  horse-power,  it  would  now  require  130.  The  higher  the 
velocity  of  the  jet  the  less  the  efficiency,  unless  the  speed  of  the  ship  is  increased  at 
same  rate. 

We  thus  find  that  to  give  the  jet  propeller  a  chance  we  require  to  move  a  very 
large  volume  of  water  at  a  speed  above  that  of  the  vessel,  and  the  centrifugal  pump 
seems  to  be  the  best  machine  for  moving  these  large  quantities  at  low  pressure.  Now, 
the  steam  turbine  coupled  to  a  modern  centrifugal  pump  would  be  something  very 
different  to  the  engines  and  pump  used  in  the  early  tests  just  referred  to.  80  per 
cent,  efficiency  can  be  realised,  that  is,  100  horse-power  turbine  pump  will  give  80  in 
the  water  horse-power.  We  cannot  in  this  place  enter  into  the  whole  question  of 
centrifugal  turbines  and  ship  resistances;  we  are  considering  water  jet  fluid-on-fluid 
engines. 

The  next  observation  to  be  made  on  the  subject  is  that  the  pump  ought  not  to 
throw  the  water  out  through  the  jets  directly.  The  object  of  the  pump  is  to  produce  the 
desired  pressure  on  the  water,  and  for  this  purpose  the  water  when  it  leaves  the  pump 


Jet  Propellers  107 


should  be  delivered  to  a  chamber  or  tank  through  widely  diverging  nozzles,  so  that  it  is 
without  agitation  brought  to  rest  or  to  a  very  slow  motion. 

The  propulsion  is  due  to  the  reaction  of  the  jets,  to  the  unbalanced  pressure  of  the 
water  in  this  tank.  If  we  have  a  tank  of  water  maintained  at  5  or  6  Ibs.  pressure,  and 
open  a  hole  in  one  side  2000  square  inches  in  area,  we  get  an  unbalanced  pressure  of 
6  x  2000  of  12,000  Ibs.  on  the  opposite  side  of  the  tank  to  the  opening,  and  that  is  the 
force  which  propels  the  ship. 

By  careful  design  an  efficiency  as  high  as  that  of  the  screw  propeller  may  be 
expected.  At  any  rate,  it  is  worth  investigating  again  practically,  whether  with  modern 
steam  turbines  driving  modern  centrifugal  or  screw  pumps,  and  with  fluid-flow  and 
pressures  directed  and  adjusted  on  modern  scientific  principles,  that  the  jet  is  not  a 
better  instrument  than  the  screw  for  propulsion.  The  steam  turbine  has  so  much  to 
recommend  it  for  ship  propulsion  ;  yet  its  full  advantage  can  never  be  realised  on  small 
high  speed  screws,  and  to  gear  down  to  large  low  speed  screws  would  certainly  be  a 
step  backwards. 

High  speed  is  the  order  of  the  day,  and  the  higher  the  speed  the  better  for  jet 
propelled  vessels,  whereas  at  high  speeds  the  screw  falls  off  in  efficiency.  The  weight 
and  space  occupied  would  be  much  less,  and  the  advantages  of  having  no  outside 
propeller  liable  to  be  lost  or  damaged,  and  no  tunnel  shafting,  are  not  to  be  despised. 

The  problem  would  be  still  further  simplified  if  an  efficient  steam  jet  could  be  used 
to  propel  these  large  volumes  of  water.  The  pumps  and  turbines  would  then  be  abolished 
also.  But  water  jets  propelled  by  steam  jets  are  very  inefficient,  pretty  much  for  the 
same  reasons  that  the  jet  propeller  failed  of  old.  The  steam  has  a  speed  of,  say,  1500  in 
an  injector  cone,  and  the  water  to  have  any  efficiency  would  require  to  move  at  a  large 
fraction  of  this  speed  to  get  economy  ;  but  no  water  jet  can  be  induced  to  move  at  such 
velocities.  At  170  Ibs.  pressure  the  water  would  issue  from  the  delivery  cone  at  8  ijz^o 
=  120  feet  per  second,  so  that  if  the  steam  jet  in  the  injector  flowing  out  at  1500  or  more 
per  second,  succeeds  in  only  imparting  230  feet  per  second  to  the  jet  from  the  combining 
cone,  it  will  feed  the  boiler  ;  but  230  is  a  small  fraction  of  1500.  For  boiler  feeding 
this  inefficiency  matters  not.  The  whole  steam,  with  all  its  heat,  minus  that  radiated 
and  conducted,  and  other  losses,  re-enters  the  boiler,  so  that  heat  efficiency  does  not 
matter. 

Theoretically,  the  velocities  imparted  should  be  inversely  as  the  weights  in  motion. 
If  i  Ib.  of  steam  flowing  at  1260  feet  per  second  struck  n  Ibs.  of  water,  the  result 
should  be  12  Ibs.  of  water  moving  at  100  feet  per  second,  and  so  the  kinetic  energy  of 
the  12  Ibs.  of  water  at  100  feet  would  be  1200,  same  as  i  Ib.  of  steam  at  1200  feet; 
for  the  total  momentum  before  impact  must  equal  the  total  momentum  after  impact. 

If  this  could  be  realised  in  practice,  then  it  would  be  useless  to  go  on  making 
reciprocating  rotary  or  turbine  steam  engines.  A  Pelton  wheel  driven  by  this  ideal 
water  jet  would  far  and  away  excel  the  lot.  But  the  steam  condenses  instantly,  and  so 
softens  the  blow  of  impact,  and  the  water  has  considerable  inertia,  so  that  it  lags  behind 
the  rushing  jet.  Consequently,  a  steam  jet  as  a  water  lifter  is  a  poor  affair  from  an 
economical  point  of  view. 

Recently  Penberthy  made  some  improvement  in  the  direction  of  applying  the  De 
Laval  cone  to  injectors.  In  all  early  injectors  and  water  jet  lifters  the  steam  cone 
converges  to  the  very  end  ;  but  some  makers  commenced  to  diverge  the  cone  a  little, 
as  shown  in  Fig.  126,  evidently  feeling  their  way  cautiously.  Penberthy  has  carried  this 
diverging  of  the  steam  cone  still  further,  as  shown  in  Fig.  124,  in  his  latest  injectors  and 
water  lifters,  with  considerable  improvement ;  how  much  we  cannot  say,  for  it  is  very 
difficult  to  get  reliable  information  about  jet  pumps  and  injectors. 

However,  I  made  some  experiments  myself,  using  properly  designed  diverging 
steam  cones,  and  thereby  more  than  doubled  the  water  lifted  by  the  same  steam 
consumpt.  The  reason  is  that  the  steam  has  a  velocity  nearly  double  of  that  issuing 


io8 


Modern   Engines 


from  a  converging  nozzle,  and  the  heat  has  been  utilised  more  efficiently  before 
condensation. 

We  have  seen  that  compound  injectors  have  been  used  to  feed  high  pressure  boilers 
at  high  temperatures. 

A  compound  water  lifter  with  several  nozzles  in  series  has  also  been  devised  whereby 
enormous  velocities  could  be  obtained.  The  water  is  started  from  rest  in  the  first 


FIG.  135. — Multiple  Nozzle  Water  Lifter. 

cone,  accelerated  in  the  second,  third,  and  so  on,  until  it  acquires  a  velocity  approach- 
ing that  of  the  steam  jet  in  the  last  one  ;  it  is  hoped  that  an  efficient  water  lifter  will 
result,  water  being  accelerated  in  stages  beginning  with  a  small  jet  of  steam.  That  is, 
instead  of  all  the  steam  passing  in  one  annular  jet  of,  say,  T\j-inch  sectional  area,  it  is 
passed  in  five  each  -^  inch  area,  or  three  of  •£$  inch  each.  The  cones  are  reduced  in 
proportion  as  the  velocity  is  increased  ;  it  is  shown  in  section,  Fig.  135. 

In  recent  tests  the  actual  results  of  a  turbine  centrifugal  pump  combination  for 
water  pressure,  the  following  table  of  results  was  obtained.  It  shows  what  might  be 
done  now  with  jet  propellers  with  efficient  pumps. 


TABLE  XL— RESULTS  OF  TESTS  WITH  DE  LAVAL  STEAM  TURBINE  PUMPS. 


Type  of  Turbine 
Pump. 

Revolutions 
per 
Minute. 

Height  of 
Suction 
in  Feet. 

Height  of 
Delivery 
in  Feet. 

Quantity  of  Water 
delivered  per 
Second-gallons. 

Water 
Horse- 
power. 

Brake 
Horse- 
power. 

Efficiency. 

50  horse-power 

^| 

duplex  pump 
coupled       in 

1500 

16.4 

16.4 

63.5 

37.87 

50.3 

0-753 

parallel    . 

J 

635  Ibs.  of  water  raised  32.8  feet  =  37  horse-power  in  the  water. 

The  pressure  of  the  jet  corresponding  to  the  height  would  be  15  Ibs.,  the  velocity 
=  8  ^32.8  =  5.74  x  8  =  45. 76  feet.  The  quantity  of  water  is  about  10  cubic  feet,  velocity 

45  feet ;  hence  —  =0.22  square  feet,  section  of  jet  31.68  square  inches. 

45 

It  is  intended  only  in  this  brief  discussion  to  put  the  jet  propeller  in  its  true  position. 
Because  some  engineers  are  quite  satisfied  with  screw  propellers  and  unreasoningly 
refuse  to  consider  anything  else,  that  is  no  reason  why  the  case  for  other  propellers 
should  not  be  put  fairly  before  those  of  a  more  inquiring  and  enterprising  disposition. 
Figures  can  only  demonstrate  the  feasibility  of  the  jet  system,  practice  alone  can  decide 
for  or  against  it ;  and  what  practical  tests  have  been  made  were  made  with  machinery 
— certainly  not  the  best  at  the  time,  and  far  inferior  to  what  would  be  employed  to-day 
to  make  practical  trials.  The  subject  will  be  more  fully  discussed  under  "  Marine 
Engines." 


Jet  Propellers 


109 


TABLE  XII.— HORSE-POWER  OF  i  CUBIC  FOOT  OF  WATER  PER  MINUTE  UNDER 

HEADS  FROM  i  TO  uoo  FEET. 


Head  in 
Feet. 

Horse-power. 

Head  in 
Feet. 

Horse-power. 

Head  in 
Feet. 

Horse-power. 

Head  in 
Feet. 

Horse-power. 

i 

.0016098 

170 

.273666 

330 

•531234 

480 

.772704 

20 

.032196 

180 

.  289764 

340 

•547332 

490 

.788802 

3° 

.048204 

190 

.305862 

350 

•563430 

500 

.804900 

40 

.064392 

200 

.321960 

360 

•579528 

520 

.837096 

5° 

.080490 

210 

•338058 

37° 

•595626 

54° 

.869292 

60 

.096588 

2  2O 

•  354^6 

380 

.611724 

560 

.901488 

70 

.112686 

230 

•370254 

390 

.627822 

580 

•933684 

80 

.128784 

240 

.386352 

400 

.643920 

000 

.965880 

90 

.  144892 

250 

.402450 

410 

.660018 

650 

.046370 

IOO 

.160980 

260 

.418548 

420 

.676116 

700 

.126860 

no 

.177078 

270 

.434646 

430 

.692214 

750 

.207350 

120 

.193176 

280 

•450744 

44° 

.708312 

800 

.287840 

130 

.  209274 

2OX> 

.466842 

450 

.724410 

900 

.448820 

140 

.225372 

300 

.482040 

460 

.740508 

IOOO 

.609800 

ISO 

.214170 

310 

.499038 

470 

.756606 

IIOO 

.770780 

160 

•257568 

320 

•S'S^S 

TABLE  XIII.— SHOWING  HEAD  AND  PRESSURES  OF  WATER. 


Head 

Pressure  of 

Head 

Pressure  of 

of 

Head  of 

Head  of 

Head  of 

Water  in 

of 

Head  of 

Head  of 

Head  of 

Water  in 

Water 

Water 

Water  in 

Water  in 

Lbs.  per 

Water 

Water 

Water  in 

Water  in 

Lbs.  per 

in 

in  Yards. 

Fathoms. 

Metres. 

Square 

in 

in  Yards. 

Fathoms. 

Metres. 

Square 

Feet. 

Inch. 

Feet. 

Inch. 

5 

1.66 

0.83 

1.52 

2.16 

185 

61.6 

30.8 

56.3 

80.  i 

10 

3-33 

1.66 

3-04 

4-33 

190 

63-3 

31-6 

57-9 

82.3 

15 

5.00 

2.50 

4-57 

6.49 

195 

65.0 

32.5 

59-4 

84.4 

20 

6.66 

3-33 

6.09 

8.66 

200 

66.6 

33-3 

60.9 

86.6 

25 

8-33 

4.16 

7.62 

10.80 

205 

68.3 

34-i 

62.4 

88.8 

30 

IO.OO 

5.00 

9.14 

12.90 

2IO 

70.0 

35-o 

64.0 

90.9 

35 

n.6o 

5-83 

10.60 

15.10 

215 

71.6 

35-8 

65-5 

93-i 

40 

13-3 

6.66 

12.  1 

17-3 

2  2O 

73-3 

36-6 

67.0 

95-3 

45 

15.0 

7-5° 

13.7 

19.4 

225 

75-o 

37'5 

68.5 

97-4 

5° 

16.6 

8-33 

15.2 

21.6 

230 

76.6 

38-3 

70.1 

99.6 

55 

18.3 

9.16 

16.7 

23-8 

235 

78.3 

39-1 

71.6 

101.8 

00 

20.  o 

IO.O 

18.2 

25-9 

240 

80.0 

40.0 

73-i 

103.9 

65 

21.6 

10.8 

19.8 

28.1 

245 

81.6 

40.8 

74.6 

106.  i 

70 

23-3 

11.6 

21.3 

30-3 

250 

83-3 

41.6 

76.2 

108.3 

75 

25.0 

12.5 

22.8 

32-4 

255 

85.0 

42-5 

77-7 

110.4 

80 

26.6 

J3-3 

24-3 

34-6 

305 

101.6 

50.8 

92-9 

132.1 

85 

28.3 

14.1 

25-9 

36.8 

310 

103.3 

51.6 

94.4 

134-3 

90 

30.0 

15.0 

27.4 

38-9 

3!5 

105.0 

52.5 

96.0 

136.4 

95 

31.6 

15-8 

28.9 

41.1 

320 

106.6 

53-3 

97-5 

138.6 

IOO 

33-3 

16.6 

30-4 

43-3 

325 

108.3 

54-  ! 

99.0 

140.8 

!°5 

35-o 

»7-5 

32.0 

45-4 

330 

I  IO.O 

55-0 

100.5 

142.9 

no 

36-6 

18.3 

33-5 

47.6 

335 

in.  6 

55-8 

1  02.  i 

I45-1 

U5 

38.3 

19.1 

35-o 

49-8 

34° 

"3-3 

56.6 

103.6 

H7-3 

120 

40.0 

20.  o 

36-5 

5x-9 

345 

115.0 

57-5 

105.1 

149.4 

!25 

41.6 

20.8 

38.1 

54-i 

350 

1  16.6 

58.3 

1  06.  6 

151.6 

I30 

43-3 

21.6 

39-6 

56.3 

355 

118.3 

59-1 

108.2 

153-8 

'35 

45-o 

22.5 

41.1 

58-4 

360 

I2O.O 

60.0 

109.7 

155-9 

140 

46.6 

23-3 

42.6 

60.6 

365 

121.  6 

60.8 

III.  2 

158.1 

"45 

48.3 

24.1 

44.1 

62.8 

37° 

123.3 

61.6 

II2.7 

160.3 

J5o 

50.0 

25.0 

45-7 

64.9 

375 

125.0 

62.5 

"4-3 

162.4 

'55 

51.6 

25.8 

47-2 

67.1 

380 

126.6 

63-3 

115.8 

164.6 

160 

53-3 

26.6 

48.7 

69-3 

385 

128.3 

64.1 

"7-3 

166.8 

'65 

55-0 

27-5 

50.2 

71.4 

390 

130.0 

65.0 

118.8 

168.9 

170 

56-6 

28.3 

51-8 

73-6 

395 

I3I.6 

65.8 

120.3 

171.1 

'75 

58.3 

29.1 

53-3 

75-8 

400 

133-3 

66.6 

121.9 

173-3 

180 

60.0 

30.0 

54-8 

77-9 

I  10 


Modern  Engines 


THE  CENTRIFUGAL  PUMP 

This  useful  apparatus  might  come  under  the  head   of  pumps,  but  as  its  action 
depends  on  fluid  velocities  and  pressures  it  may  be  as  well  to  include  it  in  this  chapter. 

The  principle  of  the  machine  has  been  given  in  its 
simplest  form  by  Professor  Goodere,  as  follows. 

Conceive  a  ring  threaded  on  a  rod,  pointing 
towards  and  at  right  angles  from  a  shaft,  and 
revolving  about  it.  We  know  that  the  rod  will 
continually  press  the  ring  in  a  line  perpendicular  to 
the  rod.  The  ring  will  tend  always  to  go  forward 
in  a  straight  line. 

We  have  now  to  refer  to  a  simple  experiment 
in  the  geometry  of  motion.  Let  a  circular  disc 
(Fig.  136)  be  rotated  about  its  centre  C,  mark  that 
centre  with  the  point  of  a  pencil,  and  then  draw 
the  pencil  rapidly  from  the  centre  outwards  to  the 
circumference.  A  curve  will  be  traced  on  the  disc, 
FIG.  136.— Theoretical  Pump  Experiment,  which  will  take  the  form  CPQ  if  the  disc  rotates 

slowly,  or  will  become  more  spiral  in  character,  as 

shown  by  CRST,  when  the  velocity  of  rotation  is  increased.  The  pencil  moves  radially 
in  a  straight  line,  but  it  traces  a  curve  by  reason  of  the  increasing  linear  velocity  of 
each  point  in  the  circle  as  we  pass  from  the  centre  outwards.  Our  conclusion  is, 
that  a  curved  rod  will  act  more  effectively  than  an  inclined  rod,  and  that  if  the 
curvature  be  regulated  to  the  velocity  of  rotation  a  sustained  and  uniform  push  may  be 
maintained  on  each  portion  of  water 
as  it  passes  from  the  centre  to  the 
circumference. 

In    constructing   a    pump    on 


FIG.  137. — Centrifugal  Pump. 


FiG.  138. — Construction  of  Centrifugal  Pump  Blades. 


this  principle  we  begin  with  a  circular  disc  AB,  shown  in  section  (Fig.  137),  which 
receives  the  water  pressure  on  both  sides.  This  is  an  example  of  balanced  pres- 
sure, and  the  friction  is  correspondingly  reduced.  The  disc  forms  the  central 
division  of  a  hollow  circular  box,  the  water  enters  on  both  sides,  as  shown  by  the 
arrows,  and  is  forced  outwards  by  the  curved  vanes,  the  three  successive  types  of 
vane  are  (i)  radial,  (2)  inclined,  (3)  curved.  In  a  pump  by  Mr.  Appold  the  diameter 
of  the  case  is  12  inches,  that  of  the  central  opening  is  6  inches,  also  there  are  6  arms, 


Centrifugal  Pumps  1  1  1 

curved  backwards  and  terminating  nearly  in  a  tangent  to  the  circumference  of  the 
bounding  circle. 

The  pump  is  set  into  rapid  rotation  between  flat  cheeks  at  the  bottom  of  a  pipe, 
the  circumference  of  the  box  being  open  to  the  inside  of  the  pipe,  and  the  centre  being 
open  to  the  supply  of  water.  The  height  to  which  they  lift  is  equal  to  the  square  of  the 
peripheral  speeds  in  feet  per  second. 

To  lift  the  water  to  any  given  height  theoretically  it  must  be  given  a  centrifugal  force 
equal  to  >j2gH  where  H  is  the  height,  or,  approximately,  8  \/H.  To  obtain  this  force 
the  speed  of  the  periphery  of  the  fan  blades  must  be  run  at  speeds  depending  upon  their 
curvature  and  the  angles  which  they  make  with  the  outer  and  inner  peripheries.  The 
diagram  Fig.  138  shows  the  usual  geometrical  construction  and  parallelograms  for 
the  entering  ends  and  leaving  ends  of  the  blades.  Referring  to  the  diagram 
Fig.  138,  the  speed  of  the  blade  at  A  depends  upon  the  angle  <£  between  the  pro- 
longation of  the  blade  A^  and  a  tangent  with  the  circle  where  the  blade  terminates. 
This  tangent  A^  is  proportional  to  the  peripheral  speed.  The  angle  (j>  varies  in  practice 
from  1  5°  to  90°  ;  and  in  a  pump  with  a  proper  volute  the  velocities  V,  instead  of  being 
equal  to  \/2£-H,  are  — 

<£      =        V 
90°     =     0.83  \/2 

45°     =     °-94      > 

30°     =      1.03       , 

20°     =     1.89      , 

15°     =      1-355    i 

In  the  case  of  a  pump  with  a  diffuser  or  whirlpool  chamber  we  take  into  account  the 
inner  radius  and  outer  radius  of  the  4  blades  rv  r2  ;  and  we  take  two  ratios  of  these 

radii  as  examples  —  first,  where  —  1  =  |  ;  second,  where  —  1  =  f. 


without  a  diffuser  or  diverging  delivery. 


45°     =     0.9  =     0.885 

30°     =      i.o  =     0.98 

15°     =      i-33  =      i." 

Without  going  into  all  minute  corrections  and  coefficients  included  in  the  mathematical 
treatment,  we  can  indicate  the  calculated  dimensions  of  a  centrifugal.  It  may  be  first 
pointed  out  that,  as  shown  in  above  tables,  as  angle  </>  decreases  or  increases,  so  does 

f  _ 

the  speed.    With  angle  =  30°  and  -f"f,  the  speed  is=  \/2£-H  ;  or  at  15°,  V=  i. 

r 


An  angle  of  90°  may  and  has  been  used  without  decreasing  the  efficiency,  but 
lowering  the  speed. 

The  head  of  water  maintained  by  a  centrifugal  with  vanes  radial  at  the  rim  is  found 

V2 
practically  by  h  =  —  .     h  =  head  in  feet,  V  =  velocity  of  wheel  rim  in  feet,  ^-=32.2  acceler- 

o 

V2 
ating  force.     And  not  to  the  usual  theoretical  formula  h=  —  . 

2g 

This  is  due  to  the  fact  that  the  water  receives  two  impulses  in  two  directions  from 
the  fan.  The  true  centrifugal  impulse  is  radial  along  the  vanes,  and  a  tangential 
impulse  whirling  it  round.  The  velocities  of  the  water  in  each  direction  at  the  moment 
it  leaves  the  wheel  are  equal  to  the  peripheral  velocity.  The  resultant  of  the  two 

V2  V2 

impulses  and  two  directions  is  that  of  the  two  components  ;  hence  the  k  =  —  x  2  =  —  . 

*g  S 


I  12 


Modern  Engines 


V2 
Therefore  the  head  may  be  greater  than  that  equal  to  — ;     but    owing    to    friction 

o 

of  water  and  obstructions  to  flow  the  calculated  head  is  never  attained  in 
practice. 

By  curving  the  blades  back  the  ratio  between  head  and  velocity  of  wheel  is  altered 
considerably,  as  will  be  seen  in  the  tables. 

The  efficiency  in  all  but  the  lowest  lifts  is  above  60  per  cent.  And  by  careful 
design  and  good  workmanship  over  80  per  cent,  has  been  obtained  in  lifts  of  20 
to  40  feet. 

The  lift  of  a  pump  is  limited  by  the  highest  circumferential  speed  at  which  the  fan 
may  be  run,  so  that  when  the  lift  exceeds  40  to  50  feet  it  is  necessary  to  put  pumps  in 
series.  And  when  we  require  both  high  lifts  and  high  values  in  gallons  per  minute  we 
must  put  them  in  parallel. 

The    radius    r^   of    a    fan    is    limited    by   the   revolutions    per   minute,    and    the 


FIG.  139. — Centrifugal  Pump. 


FIG.  140. — French  Design  of  Pump. 


speed  in  feet  of  the  circumference  of  rr  The  inlet  for  water  is  limited  by  the 
value  of  r2. 

With  a  given  speed  both  H  and  Q  are  limited,  and  if  the  limit  of  H  is  exceeded, 
turbines  are  put  in  series  ;  if  Q  is  exceeded,  then  they  are  put  in  parallel. 

For  instance,  suppose  a  centrifugal  to  lift  36  feet,  and  V  the  speed  in  feet  of  the 
outer  circumference  of  the  fan,  and  that  V=  \lgh=  ^32.2  x  36  =  34  feet ;  the  revolutions 

per  second  are,  say,  5.     Then  the  circumference  must  be  —  =  6.8  feet,  or  26  inches 

0 

y  i 

diameter.     The  ratio  —  being  =  -;  ^1  =  13  inches;  r2  =  8.6  inches.     The  velocity  of  inlet 
rz  2 

at  the  radius  rz  at  the  fan  even  as  high  as  22.5  feet  would  give  a  possible  delivery  of 
only  10.4  cubic  feet  per  second  as  the  maximum  at  that  speed  and  lift ;  hence  we  would 
require  to  parallel  the  pump  with  another  if  more  water  was  required,  and  the  higher 
the  speed  the  sooner  the  limit  to  the  capacity  of  the  pump  is  reached. 

As  rz  cannot  be  increased  without  loss  of  efficiency,  increasing  the  output  by  that 

means  is  restricted,  as  the  efficiency  falls  off  rapidly  with  decreasing  values  of  ^X 


Centrifugal   Pumps  113 

Fig.  139  shows  an  elevation  in  section  of  the  usual  construction,  with  curved  pump 
blades.  The  water  enters  at  both  sides,  and  thus  balances  the  pressures.  The  angle  <£ 
in  this  case  is  about  15°.  Fig.  140  shows  an  elevation  in  section  of  the  huge  pumps 
erected  in  Egypt  by  the  French,  in  which  the  angle  <£  is  90.  They  are  slightly  curved 
the  opposite  to  that  in  Fig.  139,  but  not  radial.  A  few  particulars  may  be  of  interest. 
The  shaft  is  vertical,  and  the  water  enters  by  the  lower  side  only.  The  fan  is  much 
like  an  inward  and  radial  flow  turbine  wheel,  like  the  Hercules  wheel  reversed  ;  if  that 
wheel  (Fig.  77)  were  driven  by  power  and  the  lower  end  dipped  into  water,  the  water 
would  be  scooped  up  vertically  and  thrown  out  radially, — that  is  the  action  of  these 
pumps.  Their  lift  is  10  feet,  and  the  water  lifted  212  cubic  feet  per  second  ;  the  speed 
is  32  revolutions  per  minute.  The  outer  diameter  is  12.446  feet ;  circumferential 


velocity,  20.8  feet  per  second  =  o. 82  *j2g-H,  a  figure  which  does  not  at  all  agree  with 
mathematical  deductions  ;  the  outer  case  is  19  feet  8  inches  diameter.  The  mouthpiece 
of  the  volute  is  5  feet  3  inches. 

The  useful  work  done  by  the  pump  is  65  per  cent,  of  the  indicated  horse-power  ; 
coal  consumption,  3.85  Ibs.  per  pump  horse-power  per  hour. 

Now,  looking  to  this  result  and  the  results  of  closely  reasoned  and  calculated 
pumps  with  volute  curves  and  everything  according  to  mathematical  deductions,  which 
are  no  better,  and  in  many  cases  not  so  good,  we  come  to  the  conclusion  that  the  data 
assumed  is  either  incomplete  or  in  error. 

Most  manufacturers  accept  the  values  for  <£  and  V  as  given  above,  and,  having 

decided  upon  a  value  of  </>  for  all  their  pumps  the  same,  stick  to  it.     -i  is  a  ratio  they 

also  fix  upon  and  adhere  to,  both  being  checked  by  careful  tests  on  actual  pumps, 
The  velocity  of  influx  at  the  inlets  is  usually  8  feet  per  second,  or  a  little  more  ;  the 
velocity  of  discharge  is  from  2  to  5  feet  usually  per  second. 

The  fundamental  formulas  is  the  same  as  for  turbines.  If  the  water  leaves  the  wheel 
without  velocity,  then  if  V  is  the  velocity  of  water  in  feet  per  second  the  pressure  due 

to  each  Ib.  stopped,  or  the  pressure  required  to  start  it  up  to  the  velocity  V,  is  —  ;  and 

o 

multiplying  by  velocity  of  wheel  rim  V^   the  useful  work  per  Ib.  = l  foot-lbs.  per 

J5 

V2 
second.     The  foot-lbs.  per  Ib.  of  water  is  H= — ,  of  which  ?iH  is  given  to  the  wheel 

by  the  water  or  by  the  wheel  to  the  water ;  hence  TjH  = i,  the  fundamental  formula 

o 

for  centrifugal  pumps  and  turbines,  77  being  the  efficiency  factor. 

In  the  case  of  the  pump,  77  is  about  0.75,  and  the  fundamental  equation  H,  the  height 

to  which  the  water  is  to  be  lifted,  requires  that 1?/  — H. 

& 
Without  going  into  all  the  calculations,  we  will  take — 

Vl  as  the  speed  in  feet  of  the  rim  of  the  wheel  per  second. 

V  as  the  speed  of  the  water  due  to  head  H. 

rlt  the  outer  radius  of  wheel)  _  3 

rv  the  inner  radius  of  wheel/     ^" 

H  =  height  to  which  water  is  to  be  raised,  to  which  is  added  an  allowance  for 

pipe  friction  if  pipe  is  long. 

U  =  the  speed  of  water  in  feet  per  second  at  inlet  =  8  feet. 
B    =  diameter  of  inlet. 
Ul  =  speed  of  water  at  outlet  =  2  to  5  feet. 
B!  =  diameter  of  outlet. 
b    =area  of  outlet  of  water  on  rim  of  fan  at  rv  not  including  thickness  of 

blades. 
VOL.  i.— 8 


114  Modern  Engines 

#!  =  area  of  inlet  at  r2,  not  including  thickness  of  blades. 

Q  =  cubic  feet  of  water  delivered  per  second. 

A   =area  of  suction  pipe. 

A!  =  area  of  delivery. 

N  =  revolutions  per  second. 

Taking,  for  example,  a  pump  to  lift  32  feet  and  deliver  10  cubic  feet  per 
second,  vanes  radial  at  the  rim. 

The  pump  is  supposed  to  have  a  volute  snail  delivery  chamber,  and  either  a 
diverging  delivery  pipe  or  a  whirlpool  chamber, — that  is,  a  circular  space  surrounding 
the  rim  of  the  wheel  in  which  the  whirl  of  the  water  is  reduced  before  it  enters  the 
snail.  Let  the  following  values  be  known  : — 

U  =  8  feet  per  second  inlet 
lli  =  5  feet  per  second  outlet 
Q  =  10  cubic  feet  per  second  [known  quantities. 
H  =32  feet 

N  =  5  revolutions  per  second> 
The  peripheral  speed  will  then  be  =  V  >Jgh=  ^32.2  x  32  =  32  feet  per  second. 

The   revolutions   are   5   per   second;    hence   ^-  =  6.4,   the  circumference   at  rlf  or 

O 

24  inches  diameter.'. r^=  12  inches. 

m 

-J  =  f ;  hence  ^  =  1 2,  r2  =  8  inches,  and  V  at  rz  will  =  20  feet. 

12  O 

d,  the  breadth  of  the  opening  in  the  wheel  at  rv  = — ;)  wherein  we  multiply 

by  12  to  reduce  to  inches  ;  hence 

,              12  x  10                 ,-                          12  x  10  -     , 

o— =  0.6,  and  £x= — —  =  1.4  inches. 


/2X-3.I 
32(  -  «- 


20l 


12  12  ' 

Now,  to  find  A,  usually  we  have  the  water  entering  on  both  sides,  so  we  will  divide 

by  2  to  find  A  for  one  side.     A='°  Cubi°  feet  per  second  x  144  e  inches  for 

8  feet  per  second  x  2 

each  side  of  suction  pipe  and  side  opening  in  the  centre  of  turbine,  io|  inches.  To 
this  must  be  added  an  allowance  for  shaft  arc,  which  would  bring  the  central  openings 
to  1  1  inches,  allowing  about  8  square  inches  for  shaft. 


!  at  discharge  will  be  similarly  =  IO  *  *J^=  225  square  inches. 

.8  x  U         .8x8 

The  suction  pipe  =  --  44_2OO  square  inches. 
0.9  x8 

Thus  we  have  found  the  leading  hydraulic  dimensions.  The  irechanical  dimensions 
are  treated  under  mechanical  designs  of  pumps. 

We  will  now  illustrate  a  few  actual  examples  of  recent  results  of  tests. 

The  ordinary  belt  driven  centrifugals  and  the  direct  coupled  centrifugal  to  quick 
speed  engines  are  greatly  in  use,  especially  the  direct  coupled,  for  marine  circulation  and 
bilge  pumps.  These  are  too  well  known  to  require  space  here. 

De  Laval  pumps,  shown  in  Plate  IV.,  by  Messrs.  Greenwood  &  Batley,  driven  by 
steam  turbine,  are  of  recent  introduction.  The  high  speed  enables  considerable  lifts  to 
be  obtained,  and  two  pumps  can  be  driven,  the  one  feeding  into  the  other  in  series, 
so  that  their  pressures  are  added  ;  and  if  each  lifts  100  feet,  the  two  would  lift 
200  feet. 

They  can  also  be  joined  in  parallel.     The  following  table  gives  some  results  :  — 


Centrifugal  Pumps 


TABLE  XIV.— RESULTS   OF  TESTS   WITH   DE   LAVAL  STEAM   TURBINE   PUMPS. 


Type  of  Turbine 
Pump. 

Revolutions 
per 
Minute. 

Height  of 
Suction 
in  Feet. 

Height  of 
Delivery 
in  Feet. 

Quantity  of  Water 
delivered  per 
Second  Gallons. 

Water 
Horse- 
power. 

Brake 
Horse- 
power. 

Efficiency. 

50  horse-power 

•) 

duplex  pump 
coupled     in 

j-      1500 

16.4 

16.4 

63-5 

37.87 

5°-3 

0-753 

parallel 

J 

50  horse-power 

' 

duplex  pump 

coupled     in 

parallel 
Constructed  for 

•      1500 

16.4 

29-53 

46.3 

38.66 

48.0 

0.805 

larger     head 

of  water  than 

the  previous  . 

, 

50  horse-power 

\ 

duplex  pump 
coupled     in 

\       220O 

19.7 

137-8 

12.3 

35-22 

5°-3 

0.700 

series     . 

J 

20  horse-power 

\ 

duplex   pump 
coupled     in 

\        2315 

9.84 

85-3 

82.5 

14.27 

20.  o 

0.713 

series     . 

J 

The  general  tendency  at  present  is  to  increase  the  speed  of  everything,  and  it  may 
perhaps  be  considered  as  a  step  in  the  wrong  direction  to  reduce  the  speed  of  a  machine. 
It  may  therefore  be  interesting  to  draw  attention  to  a  machine  now  on  the  market 
which  runs  at  the  same  speed  as  the  turbine,  namely,  a  centrifugal  pump  worked  direct 
from  the  turbine  and  at  the  same  speed.  The  machine  consists  of  a  steam  turbine 
driving  one  centrifugal  pump  direct,  and  another  by  means  of  gearing.  The  slow  speed 
pump  lifts  the  water  and  presses  it  into  a  high  speed  pump,  which  in  its  turn  forces  the 
water  against  a  considerable  head.  The  following  table  shows  some  of  the  results 
obtained  by  tests  with  one  of  these  machines  : — 


TABLE   XV.— RESULTS  OF   TRIALS  WITH   A   DE   LAVAL  HIGH   PRESSURE 
TURBINE   PUMP.     "TURBINE   SPEED   PUMP." 


Height  of 
Delivery. 
Feet. 

Gallons  of 
Water 
delivered 
per  Minute. 

Water 
Horse-power. 

Lbs.  of  Steam 
per  Water 
Horse-power 
per  Hour. 

ist  Trial   .... 

312 

529 

5° 

34-2 

2nd  Trial  .... 

443 

629 

84.4 

29.0 

3rd  Trial  .... 

5°9 

529 

81.6 

3J-3 

Work  for 
condensing 

( 

640 

90.7 

30.6 

is  included. 

4th  Trial  .... 

467i 

53° 
430 

75-o 
60.9 

32.2 
35-J 

I 

286 

40-5 

43-i 

In  these  tests  the  machine  was  mounted  at  a  considerable  distance  from  the  boiler, 
and  the  admission  steam  was  consequently  supplied  to  the  turbine  through  a  considerable 
length  of  piping,  which  gives  one  reason  to  conclude  the  steam  was  wet.  Better  results 


n6 


Modern   Engines 


would  probably,  therefore,  be  obtained  with  dry  admission  steam,  and  with  a  higher 
steam  pressure.  The  condensing-  water  was  supplied  through  a  pipe  from  the  slow 
speed  pump,  and  the  machine  consequently  drove  its  own  condenser.  In  the  figures  of 
the  table,  work  for  condensing  is  therefore  included. 

To  raise  water  500  feet  by  centrifugal  force  is  an  achievement  of  no  small  moment. 

The  special  characteristic  of  the  turbine  pumps,  namely,  their  high  speed — which  is 
greatly  in  excess  of  anything  previously  known  in  connection  with  centrifugal  pumps — 
is  a  mechanical  problem  which  has  been  solved,  partly  by  an  improvement  in  the 
construction  of  the  wheel  and  packing  boxes  of  the  pump,  including  their  lubricating 
arrangements,  and'partly  by  paying  the  greatest  attention  to  execution  of  all  the  movable 
parts.  The  high  rate  of  speed  has  enabled  the  diameter  of  the  pump  wheel  to  be 
reduced,  and  consequently  the  passive  resistance  of  the  pump  has  been  greatly  lowered. 


.  141.  —  De  Laval  Turbine  Pumps  in  Parallel. 


This  circumstance,  together  with  the  fact  that  no  transmission  belts  are  used,  has 
made  it  possible  to  obtain  with  the  turbine  pumps  an  efficiency  considerably  in  excess  of 
the  results  generally  obtained  with  centrifugal  pumps. 

Owing  to  the  water  in  the  pump  running  in  a  continual  current,  self-acting  valves 
are  avoided,  and  therefore  the  turbine  pumps  are  very  easily  attended  to  and  require  very 
few  repairs.  The  turbine  pump  runs  without  any  shocks,  and  consequently  air  vessels 
are  not  required  either  for  the  suction  pipe  or  for  the  pressure  pipe. 

Another  great  advantage  of  these  pumps  is  their  absolute  safety  against  bursting. 
Should  the  pressure  pipe  suddenly  be  shut  off  during  the  time  the  pump  is  working  at 
full  speed  the  water  pressure  could  not  go  beyond  the  so-called  "centrifugal  pressure," 
which,  as  a  rule,  is  about  25  per  cent,  above  the  ordinary  working  pressure. 

The  dimensions  of  the  turbine  pump  are  small,  and  the  weight,  when  compared  with 
its  capacity,  is  low.  In  these  respects  the  De  Laval  patent  turbine  pump  has  the 
advantage  over  all  other  systems  of  direct  acting  steam  pumps. 


High  Lift  Centrifugals 


117 


To  the  larger  sized  steam  turbines,  which  are  provided  with  two  driving  shafts,  are 
coupled  two  pumps,  one  to  each  shaft.  By  arranging  these  pumps  in  such  a  manner 
that  one  of  them  draws  the  water  and  presses  it  into  the  other,  the  pressure  in  the 
delivery  pipe  of  the  latter  pump  is  doubled.  Thus  a  high  pressure  is  attained,  and 
the  efficiency  becomes  higher  than  if  the  same  pressure  were  to  be  developed  by  only  one 
pump  of  larger  diameter. 

This  pump  thus  arranged  is  especially  well  suited  for  a  stationary  fire  engine  for 
large  works,  or  wherever  the  pump  can  be  coupled  to  a  system  of  piping  provided  with 
standpipes  ;  it  is  also  suitable  as  a  floating  fire  engine,  or  as  a  mining  pump. 

For  waterworks  in  small  towns  the  high  pressure  pumps  are  particularly  well 
adapted,  in  consequence  of  their  high  efficiency  and  their  steady  pressure.  The  stuffing 


FIG.  142. — Parsons'  Turbine  Pump. 

boxes  are  provided  with  water  checks,  which  completely  prevent  the  intrusion  of  oil  into 
the  water. 

When  the  two  pumps  are  coupled  parallel — that  is  to  say,  when  both  of  them  draw  and 
deliver  the  water  at  the  same  pressure — a  most  effective  water  raising  pump  is  obtained, 
which  delivers  double  the  quantity  of  water  delivered  by  the  high  pressure  turbine  pump, 
but  only  at  half  the  pressure. 

Messrs.  Parsons  also  make  high  lift  turbo  pumps,  specially  designed  for  high 
speeds. 

Fig.  141  represents  a  De  Laval  turbine  pump  with  the  deliveries  in  parallel ;  and 
Plate  V.  a  De  Laval  turbine  pump  with  deliveries  in  series. 

Fig.  142  represents  a  Parsons'  turbine  with  one  pump  under  tests.  This  pump 
delivered  55,000  gallons  per  hour  at  165  feet  head. 


n8 


Modern  Engines 


Messrs.  Mather  &  Platt,  Manchester,  construct  pumps  with  fans  in  series  inside 
of  one  casing  instead  of  coupling  separate  fans. 

The  feature  of  this  pump  is  that  it  consists  of  one  or  more  sets  of  vanes,  or 
impellers,  each  set  running  in  its  own  chamber  but  upon  a  common  shaft,  the  delivery 
pressure  of  the  liquid  varying  directly  as  the  number  of  chambers  used.  Thus,  if  an 
ordinary  single  pump  can  deliver  water  against  a  head  of  30  feet,  the  addition  of  another 
chamber  will  give  a  final  delivery  head  of  60  feet,  while  4  chambers  will  enable  the 
pump  to  discharge  the  same  amount  of  water  against  a  head  of  120  feet. 

With  this  multiple  pump  large  quantities  of  water,  to  a  height  of  as  much  as 
150  feet,  are  delivered. 

Recently,  by  still  greater  improvements,  they  are  now  able  to  deliver  water  against 
as  great  a  head  as  200  feet  with  a  single  chamber  and  at  a  high  efficiency,  some  of  the 
larger  sizes  giving  out  the  equivalent  of  as  much  as  76  per  cent,  of  the  power  put 
into  them. 

Most  of  these  pumps  run  at  speeds  over  1000  up  to  2000  or  more  revolutions  per 
minute. 

FAN   BLOWERS   AND   EXHAUSTERS 

These  machines  are  centrifugal  pumps  for  air,  being  designed  for  much  higher 
velocities.  Air  being  so  much  less  in  weight  per  cubic  foot,  the  speeds  of  driving  are 
necessarily  high. 

If  V  =  velocity  of  the  tips  of  a  fan  in  feet  per  second,  and  P  =  pressure  in  Ibs.  per 

square  inch,  V=  ^97,300,  and  P  =  — ^— . 

77»3°° 
If  Q  =  cubic  feet  of  air  per  minute,  and  P  =  pressure  in  Ibs.  per  square  foot,  i.e.  the 


FIG.  143. — Anemometer. 


FIG.  144. — Heenan  &  Gilbert's  Fan. 


The  pressure  P  is  measured  by  a  manometer,  a  U  tube,  which  indicates 


difference  in  pressure  between  inlet  and  outlet,  then  the  horse-power  utilised  by  the  fan 

blower  =  — ^— . 
33»coo 

the  pressure  by  difference  of  the  level  of  water  caused  by  the  pressure.  The  quantity 
is  measured  by  the  anemometer,  as  shown  in  Fig.  143,  an  air  meter  by  Casella  of 
Holborn. 

The  Pitot  tube  is  an  instrument  consisting  of  a  bent  glass  tube  on  a  scale.  One  end 
at  right  angles  is  fixed  to  the  blast,  the  other  limb  is  vertical.  The  air  blast  raises  the 
column  of  water  inside  the  vertical  limb,  and  this  difference  of  level  indicates  a  certain 
velocity  of  flow,  the  depression  of  the  column  being  proportional  to  the  square  of  the  flow. 


Air  Impellers 


119 


Fans  are  made  with  all  sorts  of  blades,  and  every  maker  claims  his  as  the  best. 
Some  are  curved  backwards,  some  curved  forwards,  and  others  not  curved  at  all.  But  as 
it  is  a  centrifugal  pump  there  is  no 
doubt  the  same  reasons  for  curving 
the  blades  as  there  are  in  that  case. 
Professor  Rankine  suggested  the 
form  adopted  in  the  Heenan  &  Gilbert 

fan  shown  in  Fig.  144.     The  vanes  ^^^^ 

at  the  inlet  slice  off  the  air  and 
wedge  it  outwards,  finally  throwing 
it  off  at  full  velocity  of  the  fan  tip, 
which  is  radial.  Most  fans  deliver 
the  air  radially,  but  Rateau  in  France 
and  Mr.  Parsons  in  this  country  have 
designed  axial  flow  fans.  These 
have  the  advantage  of  being  readily 
constructed  with  fans  in  series,  so 
that  high  pressures  can  be  attained. 
Mr.  Parsons  in  this  way,  by  using  a 
long  series  of  axial  flow  fans  with 
guide  blades  between,  like  his  steam 
turbine  reversed,  has  succeeded  in 
producing  air  pressures  up  to  50  to 
60  Ibs.  per  square  inch. 

The  turbine  can  be  economically 
used  for  air  or  gas  compression. 
A  modified  form  is  illustrated  here 
attached  to  an  ordinary  steam  tur- 
bine (Fig.  145)  ;  this  particular  set  is 
capable  of  developing  from  300  to 

400  horse-power,  and  of  compressing  _^^^^^  ^_     TBHI  I 

air  to  25  Ibs.  per  square  inch.  Com- 
pressor can  be  designed  for  practi- 
cally  unlimited  pressure  by  coupling 
two  or  more  in  tandem  with  or  with- 
out intermediate  coolers,  and  where 
electricity  is  available  they  may  as 
readily  be  motor  driven. 

Large  steam  sets  are  especially 
applicable  for  blast  furnace  work  ; 
there  are  no  air  valves  to  damage  by 
heat,  and,  as  is  usually  necessary, 
the  pressure  can  be  increased  by  50 
per  cent,  temporarily  by  means  of  a 
byepass  valve  on  the  steam  engine 
admitting  high  pressure  steam  to  the 
low  pressure  parts  of  the  turbine. 

In  rock  drilling  or  mining  work, 
motor  driven  compressors  can  be  at- 
tached to  small  cars,  and  the  com- 
pressors taken  right  up  to  the  face 
The  conveyance  of  an  equal  amount  of  power  electrically  over  long  distances  is  much 
less  costly  than  by  pipes  from  large  compressors  at  bank. 


H 

b/J 

s 

I 


Air  Impellers 


The  weight  of  the  set  shown  in  the  print  is  about  7  tons  complete. 

The  Rateau  fan  wheel  for  axial  flow  is  shown  in  Fig.  147.  A  number  of  these  can 
be  threaded  on  one  shaft  driven  at  a  high  speed  and 
with  guide  passages  between,  so  that  the  pressures 
are  added  together  at  the  end  outlet.  And  as  the 
volume  of  the  air  diminishes  as  it  rises  in  pressure, 
succeeding  wheels  are  made  of  small  diameter  and  with 
fewer  blades. 

Mr.  Parsons'  wheels  are  like  his  turbine  wheels, 
with  curved  blades. 

The  Rateau  fan  lends  itself  very  nicely  to  electric 
driving. 

The  great  usefulness  of  fans  in  ventilating  mines 
is  their  most  important  work,  very  large  and  powerful 
fans  being  required  either  to  force  air  down  or  draw 
air  up  through  the  working,  to  clear  out  gases,  foul 
air,  smoke,  steam,  etc.,  and  supply  fresh  air  for  the 
miners. 

At  Clara  Vale  Colliery  a  screw  fan  driven  by  a 

steam    turbine   has   been  fitted.       It  is  illustrated  in  Fig.    146,  and  has    considerable 
interest  as  a  more  efficient  and  reliable  form  of  fan  than  the  centrifugal  form. 


FIG.  147. — Rateau  Fan. 


The  only  other  fluid  pressure  apparatus 
we  may  refer  to  in  this  chapter  is  the  air  water 
lift,  and  we  give  an  illustration  of  the  plant  in 
Fig.  148.  On  the  right  is  a  steam  driven  air 
pump  to  give  an  air  pressure  a  little  more 
than  the  pressure  due  to  the  height  of  the 
water  to  be  lifted  =  2. 3  feet  per  Ib.  of  air  pres- 
sure. The  air  is  pumped  into  a  reservoir, 
shown  like  a  vertical  boiler.  This  is  Messrs. 
Worthington's  arrangement  and  illustration 
of  the  lift  :— 

In  principle  and  operation  the  air  lift  is 
extremely  simple.  Air  is  injected  through  a 
nozzle  placed  below  the  working  water  level, 
and,  rising,  carries  water  up  with  it.  The 
submerged  parts  are  subject  to  no  wear 
whatever,  and,  except  for  corrosion,  are 
practically  indestructible,  even  when  working  in  the  gritty  water  so  fatal  to  deep  well 
pump  pistons.  The  air  compressor  and  receiver,  the  only  parts  needing  attention,  are  at 
the  surface,  and  readily  accessible.  When  proper  submergence  of  the  air  nozzle  can  be 


FIG.  148.— Air  Water  Lifter. 


12,2,  Modern   Engines 


assured  the  yield  of  a  well  previously  fitted  with  a  deep  well  pump  is  doubled  or  trebled 
by  the  use  of  the  air  lift.  The  sparkle  and  life  imparted  to  the  water  raised,  and  the 
cooling  effect  of  the  expanding  air,  make  this  method  peculiarly  suitable  for  waterworks 
purposes  ;  while,  owing  to  the  absence  of  pump  rod  and  plunger  friction  and  the  superior 
steam  economy  of  the  fly-wheel  compressor,  better  duty  can  be  obtained  than  with  the 
old  style  pump.  When  warm  water  is  to  be  raised,  its  heat,  instead  of  being  a  dis- 
advantage, is  a  source  of  increased  economy. 

A  certain  minimum  ratio  between  submergence  of  the  nozzle  and  height  of  lift  is, 
however,  essential  to  the  successful  working  of  an  air  lift. 

This  concludes  a  review  of  wind  and  water  prime  movers,  with  some  notice  of 
machines  working  on  hydraulic  and  pneumatic  principles,  which  are  not  strictly  speaking 
prime  movers,  such  as  injectors,  centrifugals,  fans,  and  fluid-on-fluid  pumps.  Yet,  as 
they  play  a  not  unimportant  part  in  prime  movers'  applications  and  operations,  they  are 
worthy  of  some  attention. 

The  hydraulic  jet  has  been  examined  carefully  and  fully,  for  it  is  more  than  likely  to 
play  a  very  important  part  in  marine  propulsion,  as  it  offers  a  solution  of  the  difficulties 
of  high  speed,  driving  engines  direct  coupled  to  screw  propellers  outside  of  the  vessel. 
The  jet  presents  some  difficulties  also,  due  to  the  fact  that  high  pressure  jets  cannot  be 
used  with  economy,  as  the  speed  of  the  jet  must  not  exceed  the  speed  of  the  vessel  by 
more  than  twice.  This  entails  using  large  quantities  of  water,  the  chief  objection  being 
the  added  weight  of  the  water  inside  the  vessel. 

On  the  other  hand,  we  have  seen  the  many  advantages  the  jet  has  over  the  screw. 


CHAPTER    III 

THE    STEAM    TURBINE 

THIS  prime  mover,  long-  the  dream  of  advanced  and  leading  scientific  engineers,  has 
at  last  reached  the  stage  of  perfection  at  which  it  can  with  confidence  be  employed 
to  replace  the  reciprocating  piston  and  cylinder  engine  of  any  but  the  smallest  size. 
The  bigger  and  more  powerful  the  steam  turbine,  the  better  it  compares  with  the  piston 
and  cylinder  engine  if  condensing  is  used.  And  even  non-condensing  Parsons'  turbines 
compare  well  with  piston  engines  non-condensing. 

Steam  turbines  are  either  of  the  pure  impulse  type,  like  a  Pelton  wheel,  or  of  the 
pressure  type  like  the  pressure  turbine,  of  which  we  may  cite  the  vortex  wheel ;  it  will 
be  observed  that  the  so-called  pressure  turbines,  are  only  partially  pressure  turbines,  for 
most  of  them  have  curved  guide  blades  in  order  to  obtain  also  the  impulse  due  to 
change  of  motion.  The  De  Laval  turbine  is  purely  an  impulse  turbine,  the  steam  being 
thrown  at  the  highest  possible  velocity  on  the  curved  blades  of  the  wheel,  where  its 

V2 
kinetic  energy  is  converted  on  the  blades  =  —  per  Ib.  of  steam. 

*g 

In  Parsons'  turbine  the  steam  acts  by  its  velocity  being  arrested  on  the  movable 
blades  in  the  same  way,  and  also  by  its  pressure  reacting  as  it  leaves  the  movable  blades. 
Flowing  from  one  wheel  to  the  next,  its  velocity  is  gradually  absorbed  in  each,  and  it 

mV2 
expands  from  one  into  the  other  wheel.     The  kinetic  energy  = taken  for  each  wheel. 

2S 

There  is  the  third  turbine,  a  purely  pressure  turbine  ;  the  original  of  which  was  Hero's 
turbine,  in  which  the  motion  and  power  is  due  entirely  to  unbalanced  pressure.  The  first 
patent  for  this  type  was  granted  in  1784  to  an  engineer  with  the  name  of  Wolfgang  de 
Kempelen.  As  a  matter  of  fact,  there  is  no  material  difference  between  the  impulse  and 
reaction  turbines,  so  that  only  two  types  may  be  considered. 

As  the  steam  turbine  has  come  to  be  a  practical  prime  mover  of  great  im- 
portance, we  may  briefly  review  its  rise  and  progress.  That  it  will  be  much 
improved  upon  in  construction  is  beyond  a  doubt,  and  some  of  the  earlier  pro- 
posals may  still  come  forward  and  claim  attention.  It  is  as  well  to  know  what  they 
are  or  were. 

To  consider  them  in  their  order  of  time  would  be  of  no  service.  We  will  consider 
them  as  a  class  at  a  time,  beginning  with  the  Hero  turbine,  which  may  yet  be  of  service. 
Presently  the  difficulty  with  this  type  is  the  high  speed  required  of  the  wheel  to  obtain 
anything  like  efficiency  ;  there  is  also  the  difficulty  of  getting  a  steam-tight  joint  at  the 
admission  orifice  for  the  steam  into  the  wheel  at  very  high  speeds,  and  a  third  difficulty 
is  to  get  a  wheel  made  strong  enough  to  stand  the  strains  of  centrifugal  force  at  these 
high  speeds. 

Fig.  149  illustrates  the  Hero  engine  in  its  simplest  form.  Little  toys  in  this  form 
were  common  at  one  time,  made  of  glass.  A  brass  or  copper  hollow  ball,  with  a  neck 

123 


124 


Modern   Engines 


like  a  door  knob,  has  two  arms  at  right  angle  to  the  axis  attached  to  the  neck  ;  it  is 
pivoted  at  the  bottom,  and  guided  at  the  top  by  a  stem.  On  applying  a  flame  to  the 
bottom,  steam  is  generated,  which  in  passing  out  of  the  nozzles  leaves  an  unbalanced 

pressure  which  drives  them  backwards  in  the  opposite 
direction  to  the  steam  issue.  This  plan  of  revolving  the 
boiler  with  the  nozzles  obviates  any  difficulty  with  steam 
joints. 

De  Kempelen's  engine  was  the  first  practical  attempt 
to  apply  this  form  of  turbine  to  actual  work.  It  is  shown 
in  Fig.  150,  wherein  A  is  the  boiler,  with  a  stop  valve  C,  a 
safety  valve  B,  and  a  vertical  pipe  carrying  a  horizontal 
pipe  E,  which  is  free  to  revolve  ;  it  having  a  sleeve  joint 
as  shown  in  Fig.  151,  whereby  it  can  move  freely  and  yet 
be  steam-tight. 

At  the  extremities  of  the  horizontal  tube  a  hole  is 
made,  shown  at  DD,  through  which  the  steam  escapes. 
As  the  inside  of  the  pipe  opposite  the  holes  has  a  larger 
area  by  the  size  of  the  hole  than  the  side  with  the  hole  in 
it,  the  pipe  will  be  pushed  backwards  by  the  steam. 
Thus  if  the  size  of  the  hole  is  i  square  inch,  and  the 
pressure  10  Ibs.  per  square  inch,  then  there  will  be  an 
unbalanced  pressure  of  10  Ibs.  on  the  side  of  the  pipe 
opposite  the  hole,  which  will  propel  the  pipe  in  that 
direction  away  from  the  hole. 

Many  writers  describe  this  action  as  "reaction"  ;  but  it  is  not  reaction,  but  direct 
pressure  which  drives  the  Hero  turbine. 

The  discs  on  the  end  are  weights  for  fly-wheel  purposes.     It  will  be  evident  that 


FIG.  149. — Hero's  Engine. 
(200  B.C.). 


FIG.  150. — De  Kempelen's  Engine. 


FiG.  151. — Details  of  Steam-Tight  Joint 
of  De  Kempelen's  Engine. 


such  an  arrangement  would  be  very  limited  in  speed.     The  pipe  would  soon  reach  its 
breaking  strain  as  the  speed  increased. 

The  next  improvement  was  made  later  on  in  1849  by  Mr.  Nasmyth  of  Patricroft. 
It  is  thus  described  in  the  Practical  Mechanics  Journal,  vol.  i.,  1849  : — 


Early  Turbine 


Fig".   152  is  a  complete  longitudinal  section  of  the   steam  wheel,  with  its  frame, 
saw,  and   foundation   plate;   and  Fig.   153  is  a  transverse  section  through  the  wheel 


FIG.  152. — Nasmyth's  Turbine  Saw. 

and  waste  steam  case.  The  wheel  A  is  a  hollow  open  disc,  with  a  loose  side 
B  checked  into  it,  and  bolted  down  by  nine  bolts.  The  hollow  saw  shaft  C  is  cast  in 
one  piece  with  the  wheel,  and  is  carried  in  the  long  bearing  of  the  double  pedestal  PP, 


0\ 


FIG.  153. — Nasmyth's  Turbine  Saw,  showing  Nozzles. 

which  is  bolted  down  to  the  foundation  plate  D.  The  contrary  side  of  the  steam 
wheel  is  steadied  upon  the  conical  bearing  E,  on  the  end  of  the  supplying  steam  pipe  F, 
which  rests  between  the  adjustable  centre  G  of  the  back  pedestal  and  the  conical 


126 


Modern  Engines 


aperture  in  the  centre  of  the  side  plate  B  of  the  wheel.  The  arrows  show  the 
passage  of  the  steam  into  the  wheel  by  the  pipe  H  ;  and  the  escape  of  the  waste 
steam  and  condensed  water  by  the  upper  and  lower  pipes  I  and  K,  connected  with 
the  outer  casing  of  the  wheel  L.  A  compensating  spring  is  cleverly  arranged  in  a 
prolongation  of  the  steam  pipe  F  to  counterbalance  the  pressure  of  the  steam 

upon  the  area  of  its  ingress 
opening  at  M.  A  helical  spring 
N  is  placed  in  the  open  end 
of  the  pipe,  so  as  to  abut 
against  the  closed  end  of  the 
pipe  M.  This  spring  is  acted 
upon  by  a  short  sliding  block, 
urged  forward  by  the  adjusting 
centre  G  ;  in  this  way  it  is  com- 
pressed to  such  an  extent  that 
its  reaction  will  just  compensate 
for  the  steam  pressure  upon  the 
supplying  area,  and  so  prevent 
the  possibility  of  undue  friction 
upon  the  conical  joint  of  the 
side  plate  of  the  steam  wheel. 

The  waste  steam  case  L  is 
cast  in  two  halves,  bolted  to- 
gether at  the  centre  by  means  of 
side  lugs,  the  whole  being  firmly 
bolted  by  flanges  at  the  bottom 
to  the  base  plate,  which  has  a 
steadying  rib  cast  on  it  to  fit 
the  interior  of  the  lower  edge  of 
the  case.  The  total  area  of  the 
four  steam  apertures  is  i^  square 
inch  ;  steam  pressure,  60  Ibs. ; 
revolutions  per  minute,  upwards 
of  2000.  The  time  taken  to  cut 
a  bar  of  the  average  section  is 
10  secortds,  and  it  is  to  this 
limited  period  of  action  that  this 
species  of  steam  propeller  owes 
its  peculiar  fitness.  For  although 
the  wheel  has  in  reality  very  little 
power,  yet  its  great  speed  ad- 
mits of  a  large  accumulation  of 
momentum  between  each  sawing 
action,  and  practically  gives  it 
ample  power  for  the  10  seconds 
duration  of  work. 

Another  wheel  designed  to 
run  a  fan  blower  was  described 
in  the  same  volume.  It  is  shown 
in  Fig.  154  in  section.  The 

steam   enters  the  centre  of  the  wheel  and  escapes  by  curved  arms,  as  shown.     The 
longitudinal  section  shows  the  hollow  shaft  through  which  the  steam  enters  the  wheel. 
It  is  evident  that  in  both  these  the  idea  of  the  design  is  to  obtain  a  wheel  which 


Watt's  Turbine 


127 


could  be  run  at  high  speeds.     Unfortunately,  in  neither  case  was  the  diameter  of  the 
wheels  stated  ;  but  2000  revolutions  is  given  as  the  speed. 

It  was  pointed  out  at  the  time  that  the  speed  of  the  wheel  would  require  to  be  some 
large  fraction  of  the  speed  of  issue  of  the  steam  from  the  nozzles  to  get  any  efficiency, 
and  that  speed  was  calculated  at  1200  per  second. 

About  that  time  much  attention  was  paid  to  steam  turbines.     Pilbrow,  the  great 
turbine  inventor,  had  made  his  experiments  and  patents 
known. 

De  Kempelen  had  evidently  seen  the  impossibility  of 
obtaining  efficiency  with  steam,  and  proposes,  but  un- 
fortunately without  illustrations,  a  method  whereby  he 
uses  the  steam  to  propel  water  alternately  from  two 
vessels.  Through  his  turbine,  he  says,  the  steam  is  to 
be  admitted  alternately  from  the  boiler  to  the  two  vessels, 
and  presses  upon  the  surface  of  the  water,  forces  it  into 
the  turbine ;  the  water  is  to  be  returned  to  the  receivers 
and  worked  hot. 

In  the  same  year  James  Watt  patented  this  same  idea. 
It  is  shown  in  Figs.  155  and  156  in  diagram.  A  vessel 
A,  B,  D,  E,  C  is  mounted  upon  a  pivot  J,  and  supported  by 
collar  K  at  upper  end.  The  vessel  is  divided  into  two, 
with  an  opening  HH  in  each  at  the  side  for  the  escape 
of  the  fluid,  and  there  are  two  clack  valves  F  and  G  for 
the  entry  of  the  fluid,  which  surrounds  the  rotating 
vessels  up  to  the  level  of  the  overflow  O.  Steam  is  sup- 
plied by  pipe  L  alternately  to  the  two  divisions  of  the 
vessel,  so  that  when  one  is  filling  up  with  fluid  the  other 
is  being  emptied  by  the  steam  pressure. 

Watt  proposed  to  use  mercury,  oil,  or  water  as  the 
acting  fluid. 

Both  these  proposals  when  examined  show  that 
they  had  hit  on  the  idea  of  the  pulsometer  in  a  primitive 
form.  In  point  of  fact,  a  pulsometer  pivoted  at  the  bottom,  and  with  its  water  inlet 
under  water  level  and  its  steam  inlet  in  a  stuffing  box  free  to  revolve,  would  constitute 
a  modern  and  more  effective  turbine  on  the  Kempelen  and  James  Watt  plans  for  fluid 
turbines.  Instead  of  the  ordinary  outlet  there  would  be  two  nozzles,  one  on  each  vessel 
for  the  ejection  of  the  water  at  a  tangent  to  the  vessels. 

Trevithick's  patent  describes  Hero's  turbine 
without  much  improvement  upon  Hero's  machine. 

Ericsson,  in  his  patent  of  1830,  shows  considerable 
improvement  upon  Hero,  as  will  be  seen  from  the  two 
figures — one  a  cross  section,  the  other  a  view  of  the 
wheel.  He  forms  conical  nozzles  either  on  the  side  of  the 
wheel,  or  on  the  outer  periphery  as  shown  at  rrly  Fig.  1 57. 

The  fixed  vanes  J  are  carried  on  a  fixed  sleeve  a  on  the  shaft,  which  moves  easily 
within  the  sleeve.  The  steam  enters  the  nozzles  from  the  outside  or  inside,  but  the 
fixed  vanes  are  always  placed  so  as  to  prevent  the  rotation  of  the  steam. 

These  fixed  vanes  reveal  the  fact  that  Ericsson  had  found  it  necessary  to  stop  the 
rotation  of  the  steam  against  a  fixture.  The  author  of  this  book  made  some  experiments 
with  a  similar  wheel  designed  for  high  speeds  in  1890,  and  found  that  without  a  set 
of  fixed  vanes  in  the  case  where  the  steam  enters  from  the  outside  and  escapes  by 
the  axis  it  was  not  possible  to  get  it ,  to  work,  for  the  steam  whirled  round  and 
round  until,  by  its  own  friction  against  the  wheel,  it  lost  its  energy  and  escaped, 


Sectional  Elevation. 
FlG.  155. — James  Watt's  Turbine. 


FIG.  156.— Steam  Inlet  of  Watt's 
Turbine. 


128 


Modern  Engines 


and  the   friction  of  the  steam  balanced  the  pressure  on   the  jet,   and   there   was    no 
motion. 

Alexander  Morton,  of  Glasgow,  the  inventor  of  the  ejector  condenser,  also  found  this 
out,  for  in  his  first  patents  he  describes  a  steam  turbine  on  Hero's 
plan,  in  which  he  used  a  series  of  concentric  wheels,  somewhat  like 
Ericsson's  wheel  (Ericsson,  by  the  way,  was  the  inventor  of  the  screw 
propeller).  The  idea  is  that  the  steam  entering  the  inner  one  will 
propel  it  by  pressure  on  the  nozzles,  then  expanding",  do  the  same  in 
the  next  outer  ring-,  and  in  the  next.  It  was  found,  however,  on  trial 
of  this  series  of  wheels,  that  the  effect  was  nothing1 ;  the  steam  simply 
expended  its  energy  in  rushing  round  in  the  opposite  direction  to 
that  which  the  wheels  ought  to  have  rotated,  and  its  friction  counter- 
balanced the  steam  pressure  on  the  outflow  nozzles.  In  his  next 

patent  we  find  fixed 
blades  inserted  to 
stop  the  rotation  of 
the  steam.  There 
are  three  wheels  con- 
centric with  diverg- 
ing nozzles  on  their 
periphery,  and  be- 
tween these  there 
are  fixed  blades  and 
an  outer  row  of 
fixed  blades  on  the 
casing  ;  these  stop 
the  whirl  of  the 
steam. 

On  examination  of  these  early 
machines  it  will  be  seen  that 
although  capable  inventors,  from 
Watt's  time  forward,  have  tried 
to  improve  upon  Hero,  they  have 
made  very  little  progress.  Von 
Rathen  made  Hero  turbines  with 
diverging  nozzles  ;  Ericsson  and 
Morton  also  employed  diverging 
nozzles,  but  a  little  reflection 
will  show  that  the  gain  to  be 
obtained  by  diverging  nozzles  in 
this  type  of  turbine  is  small  — 
in  fact,  nil.  All  of  these  in- 
ventors failed  to  grasp  the  fact 
that  the  improvements  required 
were  such  as  would  enable  the 
wheel  to  run  at  enormous  velo- 
cities at  the  steam  orifice.  We 
will  now  take  Parsons'  design 
of  pressure  turbine,  Fig.  158;  it  is  a  reaction  engine,  consisting  of  one  or  more  pairs 
of  arms  mounted  upon  a  spindle,  and  so  arranged  that  steam  is  admitted  to  the  interior 
of  the  said  arms  by  suitable  passages  in  the  spindle,  and  is  discharged  from  each  pair 
by  apertures  at  the  ends  of  the  arms  arranged  to  discharge  at  or  near  the  tangent  to  the 
circle  swept  by  the  arms. 


Parsons'  Turbines  129 

The  arms  are  arranged  within  a  hollow  case  or  series  of  cases.  In  one  con- 
struction (Fig.  158)  a  series  of  circular  cases  D,  D1,  D2  check  into  each  other  circum- 
ferentially,  and  form  one  larger  case  divided  by  partitions  into  a  number  of  chambers. 
One  spindle  passes  through  the  series  of  chambers  and  carries  upon  it  a  pair  of  arms 
in  each  chamber.  One  arm,  however,  may  be  carried  in  each  chamber  provided  with 
a  suitable  balance  piece  or  weight ;  or  any  number  of  arms  may  be  so  carried,  pro- 
vided that  balancing  is  carefully  allowed  for.  One  end  of  the  spindle  passes  through 
a  high  pressure  steam  chest  B,  and  a  number  of  grooves  turned  in  the  spindle  work 
in  a  bearing  having  corresponding  grooves ;  one  set  of  such  grooves  E  prevents 
the  high  pressure  steam  from  leaking  into  the  atmosphere  from  the  said  high  pressure 
steam  chest,  and  another  set  of  grooves  E1  prevents  the  high  pressure  steam  from 
leaking  into  the  first  chamber.  Between  the  two  sets  of  grooves  and  the  spindle 
radial  apertures  C1  are  drilled  to  a  hollow,  bored  out  or  formed  in  the  spindle. 
Similar  apertures  C2  lead  from  the  said  hollow  to  the  interior  of  the  boss  off  the 
first  pair  of  arms  ;  the  arms  A,  A1,  A2  are  cast  hollow  with  a  passage  of  uniform 
area  and  of  flattened  section.  The  exterior  is  also  of  a  flattened  section  sharpened 
towards  both  edges  in  order  to  provide  arms  capable  of  passing  rapidly  through 
the  steam  in  the  casing  without  creating  much  resistance.  That  is,  the  arms  are 
arranged  to  move  on  edge  through  the  steam  within  the  casing,  and  the  necessary 
section  is  provided  by  making  them  sufficiently  wide.  These  arms  rotate  at  about  6000 
revolutions  per  minute,  and  hence  it  is  necessary  that  there  should  be  a  considerable 
margin  of  strength  to  resist  the  great  centrifugal  force.  To  provide  this  strength  the 
exterior  figure  of  each  arm  is  conical,  that  is,  the  arm  is  thicker  and  broader  at  the 
root  near  the  boss  than  it  is  at  the  extremity.  Slots  a,  a1,  a?  are  cut  in  the  edges  of 
the  arms  to  furnish  discharge  orifices  and  permit  the  steam  by  its  reaction  to  propel  the 
arms  and  hence  the  spindle.  The  steam  passing  from  these  orifices  fills  one  chamber 
of  the  casing  and  passes  thus  through  the  boss  of  the  next  arm,  which  boss  is  turned 
to  fit  a  bored  opening  in  the  wall  of  the  chamber.  A  series  of  passages  through  the 
said  boss  permit  steam  to  flow  from  the  first  chamber  into  the  interior  of  the  second 
pair  of  arms  ;  thus  the  steam  discharges  by  emission  apertures  into  the  second  chamber 
of  the  casing.  From  the  second  chamber  the  steam  passes  similarly  through  the  boss 
of  the  third  pair  of  arms,  and  by  emission  jets  to  the  third  casing,  whence  the  steam 
may  pass  to  the  fourth  pair  of  arms  and  chamber,  and  so  on. 

As  the  steam  passes  in  this  manner  from  chamber  to  chamber  through  each  pair 
of  arms  the  pressure  falls,  and  each  pair  by  reaction  adds  to  the  energy  of  rotation 
of  the  steam  wheel  or  turbine  spindle.  The  interior  of  the  passages  and  emission 
apertures  of  the  arms  are  arranged  in  continually  increasing  area  in  order  to  allow 
for  expansion. 

It  has  been  proved  that  steam  cannot  flow  at  more  than  1440  feet  per  second  from 
an  orifice,  and  that  an  expansion  of  i  to  1.63  is  sufficient  to  gain  this  velocity  ;  therefore 
in  a  compound  turbine  of  the  reaction  jet  type,  when  working  with  100  Ibs.  steam  and 
exhausting  into  the  atmosphere,  it  is  necessary  to  employ  at  least  five  sets  of  arms  in 
separate  cases,  thus  limiting  the  expansion  in  each  issue  to  under  the  above-mentioned 
ratio  of  expansion.  For  this  reason  reaction  wheels  like  Hero's  engine,  employing  one 
wheel  only,  have  not  given  good  results. 

The  boss  of  each  arm  projecting  through  the  partitions  is  arranged  as  a  nice  fit, 
and  grooves  or  serrations  may  be  turned  in  the  bored  apertures  in  the  chamber  walls  ; 
a  groove  packing  is  used  for  resisting  high  steam  pressure.  Such  a  packing  is  described 
in  Specification  of  Patent,  No.  1 120  of  1890.  To  return  to  the  turbine,  we  shall  quote  only 
two  of  the  claims  : — 

i.  A   steam   wheel   or   engine   consisting   of  a  number   of  hollow   reaction   arms 
arranged   in   sequence   in   a   number  of   chambers,    the   said    arms   having   discharge 
apertures  of  increasing  area  from  the  high  pressure  to  the  low  pressure  end. 
VOL.  i. — 9 


130 


Modern   Engines 


2.  A  steam  wheel  or  engine  comprising'  a  series  of  chambers  in  which  reaction 
arms  are  caused  to  rotate,  the  said  chambers  being  provided  with  drainage  apertures 
HH,  and  drainage  boxes  or  spaces  GG,  substantially  as  hereinbefore  described. 

A  speed  of  1400  feet  per  second  at  the  periphery  is  necessary  for  the  full  efficiency, 
whereas  none  of  these  wheels  could  with  safety  run  above  100  per  second  in  peripheral 
speed  in  feet. 

The  Hero  engine  in  the  form  shown  in  Fig.  153,  but  designed  for  a  speed  of  about 
30,000  feet  per  minute  at  the  periphery,  would  be  as  efficient  as  the  De  Laval  or 
Parsons'  turbines  without  any  special  nozzles. 

We  may  pass  over  all  the  abortive  attempts  of  many  inventors  to  make  a  successful 
Hero  turbine.  Until  1893  we  find  only  Mr.  Parsons'  patent  for  a  steam  turbine  on 
Hero's  method.  It  is  shown  in  Fig.  158,  a  longitudinal  and  cross  section.  Pilbrow, 
fifty  years  before,  had  shown  that  by  putting  turbine  wheels  in  series  a  greater  economy 


Longitudinal  Section. 

FiG.  158. — Parsons'  Turbine — Hero  Type. 


Cross  Section. 


could  be  effected,  for  the  difference  of  pressures  could  be  reduced,  and  the  velocities  also 
to  some  extent  reduced. 

Mr.  Parsons  in  this  specification  calls  the  wheels  reaction  engines  ;  strictly  speaking, 
they  are  purely  direct  pressure  wheels. 

The  reasoning  regarding  the  expansion  from  100  Ibs.  to  atmospheric  pressure 
in  five  stages — that  is,  in  a  series  of  five  wheels — is  correct  enough  ;  but  while  that 
arrangement  would  be  more  economical  in  steam  than  one  wheel,  the  necessity 
for  running  the  wheels  at  some  large  fraction  of  1440  feet  per  second  still 
remains. 

This  turbine,  in  order  to  run  at  a  much  lower  speed  than  1400  feet  per  second, 
would  require  not  five  wheels  in  series,  but  fifty,  as  the  speed  and  pressure  of  the  steam 
would  have  to  fall  by  very  small  steps  to  get  the  small  velocity  of  flow. 

The  velocity  is  equal  to  64. 4^*  for  air  with  a  density  of  0.080728  Ibs.  per 
cubic  foot,  where  x  =  inches  of  water  required  to  balance  the  difference  of  pressure 
P—p\=Pr  If  we  were  working  with  compressed  air  a  difference  of  p—  100-^  =  92, 
/>2  =  8  Ibs.,  the  water  pressure  column  to  balance  i  Ib.  =  2. 24  feet,  or  about  27  inches 
of  water. 

To  calculate  for  steam,  we  take  the  volume  of  steam  at  the  given  pressure,  and  thus 
if  the  difference  of  pressure  between  the  first  wheel  and  the  next  were  100-93  =  7,  or 
nearly  0.5  of  an  atmosphere,  at  100  Ibs.  pressure,  the  volume  of  a  cubic  foot  of  steam 


Turbine  Wheels 


is  272  times  the  volume  of  water;  hence  we  get  V  =  8^272  x  0.5  x  32  =  528  feet 
per  second.  We  would  require  to  calculate  each  step  separately  as  the  pressure 
dropped. 

It  is  thus  seen  that  to  reduce  the  speed  to  500  per  second,  or  30,000  feet  per 
minute,  would  require  a  series  of  wheels  in  which  the  steam  expanded  by  a  drop  of  less 
than  7  Ibs.  between  wheel  and  wheel  at  the  start,  and  a  less  and  less  drop  towards 
the  exhaust  for  the  volume  of  steam  at  atmospheric  pressure  equals  nearly  1800  times 
that  of  water. 

The  greatest  fall  allowable  is  at  the  high  pressure  end  of  this  series,  and  that  is 
7  Ibs.  in  this  case  ;  so  that  it  is  quite  clear  that  if  any  efficiency  is  to  be  got  out  of  a 
series  of  Hero  wheels  their  number  must  be  great,  and  the  difference  between  each  in 
pressure  small  ;  for  the  speed  in  feet  could  in  few  cases  be  allowed  to  reach  even  500 
per  second.  Mr.  Parsons  proposes  to  run  the  wheels  at  6000  revolutions  per  minute. 

Now,  if  we  allow  an  efficiency  of,  say,  half,  ^  —  =  264  feet  per  second,  or  15,840  per 


minute;  then 


=  2.64  feet  would  be  the  circumference  of  the  circle  described  by 


_ 
6,000 

the  wheels  at  the  diameter  of  the  orifices.     This  diameter  would  then  be  about  10  inches. 

The  difficulties  in  the  way  of  making 
a  turbine   successfully   on    this    plan   are 


FIG.  159. — Double  Wheels.     Hero-De  Laval. 


FIG.  160. — Double  Wheels.     Hero-De  Laval. 


many,  and  no  proposal  up  to  the  present  time  has  done  much,  if  anything,  to  over- 
come them. 

Working  with  an  inexpansible  fluid  like  water,  it  makes  an  excellent  turbine ;  the 
difficulties  begin  when  a  fluid  which  must  be  worked  expansively  is  to  be  used. 

The  best  that  can  be  done  with  it  at  present  is  to  compound  a  Hero  wheel  with  a 
purely  impulse  wheel,  that  is,  to  combine  a  Hero  wheel  with  a  De  Laval  wheel,  and  thus 
reduce  the  revolutions  by  one-half.  This  idea  occurred  to  the  author  some  two  years 
ago,  and  has  since  been  patented  by  Mr.  Parsons. 

A  diagram  showing  the  principles  of  this  turbine  is  shown  in  Fig.  159.  The  inner 
wheel  is  a  Hero  wheel  with  diverging  nozzles,  in  which  the  steam  acquires  its  maximum 
velocity  before  striking  the  outer  wheel,  with  plain  curved  blades  like  the  De  Laval 
wheel. 

If  we  take  a  De  Laval  wheel  and  place  it  face  to  face  with  a  Hero  wheel  in  which 
the  noozles  are  made  diverging  as  in  a  De  Laval  wheel,  the  two  wheels  when  steam 
is  supplied  to  the  Hero  wheel  will  revolve  in  opposite  directions  with  about  equal 
torque,  so  that  they  may  be  geared  to  one  common  shaft,  or  each  may  drive  a  separate 
dynamo. 

The  turbine  of  Mr.  Parsons  combines  two  wheels  in  this  way. 


Modern   Engines 


FIG.  161. — Pilbrow's  Double  Turbine. 


Mr.  Parsons'  patent  specification  describes  his  arrangements  of  the  double  wheel 
type  (Fig.  160)  as  follow: — 

In  fluid  pressure  turbines  of  the  De  Laval  type  the  method  of  securing  a  high 
relative  velocity  between  jet  and  bucket  with  reduced  skin  frictional  losses,  by  rotating  in 
opposite  directions  the  element-carrying  nozzles  and  the  element-carrying  buckets  or  vanes 
against  which  the  fluid  impinges,  is  substantially  as  described.  The  arrangement  is 
preferably  such  that  the  working  fluid,  after  impinging  on  the  vanes,  passes  to  the  exhaust 
without  interfering  with  the  action  of  succeeding  jets.  The  shafts  of  the  counter- 
rotating  elements  may  be  co-axial,  and 
may  respectively  carry  the  two  reacting 
parts  of  a  dynamo  machine.  Reversing 
turbines  of  this  class  may  comprise  a 
separate  set  of  nozzles  (which  may  be 
fixed),  supplied  from  a  separate  pressure 
chest,  and  adapted  to  direct  working 
fluid  against  the  reverse  sides  of  the 
buckets,  or  against  a  row  of  reversely 
set  buckets.  The  inventor  says:  "By 
my  new  method  I  produce  a  steam 
turbine  of  remarkably  simple  construc- 
tion, which  in  operation  allows  great  reduction  in  the  losses  from  the  skin  frictional 
resistance  ;  and  this  renders  the  single-expansion  type  for  the  first  time  admissible  for 
direct  coupling  to  dynamos  or  screw  propellers  or  other  purposes,  where  the  speed 
of  revolution  is  moderate.  Apart  from  power  saved  in  gearing  dispensed  with,  such 
turbines  have  only  one-fourth  the  disc  stresses  and  one-fifth  the  skin  resistance  of  the 
simple  form." 

This  principle  of  construction  I  have  carefully  investigated,  and  my  conclusions  are, 
that  it  introduces  insurmountable  mechanical  difficulties.  It  only  reduces  the  revolu- 
tions by  one-half,  while  it  at  the 
same  time  introduces  a  hollow 
wheel  with  steam  inlet  around  the 
shaft,  subject  either  to  much  leakage 
or  great  friction. 

Pilbrow  again  anticipated  this 
placing  of  two  wheels  together  in 
order  to  get  smaller  speeds  or  a 
"high  relative  velocity,"  and  his 
plan  is  shown  in  Fig.  161,  in  dia- 
gram. The  steam  jet  enters  the 
first  wheel  and  propels  it  in  one 
direction,  it  then  enters  the  second 
wheel  at  full  velocity  and  propels  it  in 
the  opposite  direction,  and  the  two 

wheels  can  be  geared  together  so  that  they  add  their  power  to  one  common  shaft.  With 
the  knowledge  given  by  the  De  Laval  specification  regarding  diverging  nozzles  we  would 
now  make  the  two  wheels  as  shown  in  diagram,  Fig.  162.  In  this  turbine  the  steam  enters 
by  a  converging  jet  into  a  wheel  with  diverging  passages,  so  that  there  are  no  difficulties 
about  the  steam  inlet  as  there  is  with  a  hollow  wheel.  The  steam  in  passing  through 
the  first  wheel  propels  it  by  unbalanced  pressure,  and  also  expands  to  atmospheric 
pressure,  and  strikes  the  second  wheel  with  full  velocity  as  in  the  De  Laval  wheel ;  we 
thus  get  the  double  effect.  In  this  turbine  the  two  wheels  are  face  to  face  and  overhung 
on  the  end  of  shafts,  so  that  they  can  have  some  free  lateral  motion,  and  thus  find  their 
own  centre  of  gravity,  around  which  they  revolve  with  silence. 


Outlet  Side. 


jrniet  ^^ 
FIG.  162.— Double  Face  to  Face  Turbine. 


Turbine  Wheels  Double 


FlG.  163. — Combined  Wheels  Type  of  Turbine. 


A  diagram  of  this  turbine  is  given  in  Fig.  163,  in  which  B  is  the  one  wheel  and  C 
the  other,  mounted  on  separate  shafts  ;  D  is  the  steam  chest  and  nozzles  which  con- 
verge on  the  first  wheel  B.  The  two  wheels  are  geared  by  helical  cut  gearing1  on  to 
one  shaft,  the  one  wheel  F  being  an  external  toothed  wheel,  and  the  other  G  an  internal 
toothed  wheel ;  with  same  pitch  line  they  thus  both  drive  in  same  direction. 

This  design  is  the  author's,  and  experience  proves  it  to  be  of  considerable  advantage 
for  smaller  powers.  It  will  be  more  fully  described  later  on. 

In  the  ordinary  De  Laval  turbines,  if  we  take,  for  instance,  a  10  horse-power  machine, 
the  peripheral  speed  is  617  feet  per 
second,  the  revolutions  400  per  second, 
or  24,000  per  minute.  In  my  combined 
wheels,  in  which  the  nozzles  rotate 
backwards  at  same  speed  as  the  wheel 
goes  forward,  the  speed  of  each  wheel 
is  200  feet  per  second  and  12,000 
revolutions  per  minute.  And  as  the 
disc  stresses  are  as  the  square  of  the 
speed,  they  will  be  reduced  to  a  fourth 
of  what  they  are  in  a  single  wheel,  and 
the  skin  friction  to  a  fifth. 

The  gearing  is  objectionable  for 
large  sizes.  Another  direction  for  ex- 
periment lies  in  the  use  of  long  nozzles 
wound  into  a  scroll  on  the  periphery  of 
a  disc,  or  cut  on  the  face  of  a  disc  and 
closed  by  a  steel  disc.  The  steam 
being  continually  deflected  exerts  a 
tangential  pressure.  A  rough  test  of  this  principle  gave  fair  results,  as  also  did  a  test 
with  a  screw  cut  on  a  barrel  and  gradually  increasing  in  depth  towards  the  outlet.  The 
screw  was  cut  on  a  brass  barrel,  6  inches  diameter  outside,  5  inches  inside.  The  screw 
was  cut  with  a  square  thread  ^-inch  pitch,  the  thread  being  T\-  inch  thick,  and  the  space 
between  y\  inch  ;  the  depth  of  the  thread  was  £  inch.  After  the  barrel  was  threaded  it 
was  tapered  down  in  the  lathe  until  the  thread  at  one  end  was  only  /T  of  an^inch  deep, 

so  that  it  gave  a  long  spiral  taper- 
ing nuzzle,  tapering  16  to  i  from 
end  to  end.  A  brass  sleeve  bored 
to  the  same  taper  was  slipped  over 
the  barrel  hot,  and  shrunk  on  to  it, 
thus  closing  the  long  spiral  nozzle. 
The  barrel  was  mounted  on  a 
spindle,  one  end  of  which  was 
hollow  for  steam  admission  to  the 
narrow  end  of  the  spiral.  The 
steam  expanding  and  flowing1  along 
the  spiral  exerted  a  tangential  pres- 
sure, which  propelled  the  barrel  on  its  axis.  This  turbine  is  shown  in  Fig.  164.  It  was 
not  so  effective  as  the  scroll. 

Professor  Hewitt  tried  a  screw  form  of  turbine,  but  from  the  illustrations  given 
of  it,  of  which  Fig.  165  is  one,  the  chief  direction  of  pressure  would  be  axial  with  a 
long  pitch  screw  working  a  fixed  barrel,  whereas  it  is  tangential  pressure  which  is 
necessary  to  rotate  the  shaft. 

Mr.  Morton  tried  an  experiment  on  a  curved  nozzle  with  steam.  He  let  little  glass 
tubes  A,  B,  C,  D,  E,  and  F  into  the  inner  and  outer  curved  walls  of  the  tube  or  nozzle 


FIG.  164. — Screw  Type  of  Turbine. 


Modern   Engines 


G,  as  shown  in  Fig.   166.      The  tubes  A,  B,  and  C  on  the  greater  curved  side  were 
U-tubes,  and  had  mercury  about  half  filled  up  ;  the  tubes  D,  E,  and  F  on  the  smaller  curve 


(-B       m       rn 


FIG.  165. — Professor  Hewitt's  Screw  Type  of  Turbine. 


FIG.  166. — Morton's  Experiment. 


dipped  into  mercury.     On  blowing  steam  through  the  nozzle  a  considerable  pressure 

was  found  on  the  outer  curve,  and  a  partial  vacuum  on  the  inner  curve. 

The  position  of  the  Hero  turbine  to-day  may  be 
summed  up  by  saying  that  it  is  at  its  best  when  con- 
structed with  nozzles  diverging  and  delivering  into 
another  turbine  wheel  with  curved  buckets — these  two 
wheels  geared  to  one  shaft  or  driving  two  dynamos  in 
series  with  each  other,  and  rotating-  in  opposite  directions. 
The  reaction  turbine  is  one  in  which  the  steam 
passes  from  the  guide  blades  under  pressure,  and  with 
some  velocity  and  pressure,  so  that  the  driving  effort 
is  partly  due  to  unbalanced  pressure,  as  in  the  Hero 
machine,  and  partly  due  to  the  impulse  from  the 
weight  of  steam  thrown  against  the  curved  moving 
blades. 
The  purely  impulse  turbine,  the  De  Laval  type,  was  very  thoroughly  investigated  by 

Pilbrow,  and  his  results  given  in  his  Patent  Specification,  No. 

9658,  1843.     He  found  out  that  a  jet  of  steam  gave  a  greater 

impulse  to  a  vane  when  the  vane  was  some  distance  from  the 

orifice,  and  with  60  Ibs.  pressure  ;  he  states  that  the  best  dis- 
tance is  f  inch  ;    and  with   an  orifice  of  f  inch  diameter  he 

obtained  an  impulse  of  14  Ibs.     And  he  calculated   correctly 

that  to   obtain   efficiency  the  speed  in  feet  per  second  of  the 

vanes  would  require  to  be  1250.     Pilbrow  allowed  the  jet  to 

expand  and  acquire  a  high  velocity  before  striking  the  vanes, 

by  shifting   the  nozzle  back  until  he  obtained  "the  best  dis- 
tance from  the  orifice  ;   f  inch  from  the  vanes."      It  will  be 

seen  from  this  that  the  steam  would  have  time  and  space  to 

expand  and  acquire  velocity  before  entering1  the  wheel.     He 

also   shows  fixed  vanes   "to  lead   away  the   steam."      Their 

object  is  not  very  clear.     Pilbrow  then  put  wheels  in  series,  so 

that  the  steam  entered  first  one  wheel,  and  then  the  next,  and  so 

on  through  all  of  them.     We  have  already  referred  to  his  two 

wheels  in  series  going  in  opposite  directions  face  to  face. 

Robert  Wilson,  of  Greenock,  in  1848  patented  turbines  in 

which  the  steam  was  successively  expanded  in  one  wheel,  and   pIG- 167.— Wilson's  Turbine. 

from  wheel  to  wheel. 

A  part  section  of  the  first  form  is  shown  in  Fig.  167.     The  steam  enters  at  I,  goes 

through  the  wheel  to  the  inside,  re-enters  at  sl,  goes  through  the  wheel  to  the  outside  at 


Turbine  Wheels  in  Series 


T35 


m2,  re-enters  again  at  r2,  thence  to  »2,  and  so  on,  zigzagging  out  and  in,  as  shown  by 
the  arrows,  till  it  finally  reaches  the  exhaust. 

In  another  wheel  (Fig.  168)  Wilson  employed  concentric  rows  of  curved  vanes  alter- 
nately fixed  and  movable,  or  alternately 
fixed  on  two  discs  or  shafts  capable  of 
rotating  in  opposite  directions.  This 
turbine  has  been  resurrected  with  some 
effect  in  America  recently.  The  diffi- 
culty with  this  form  is  the  rapid  ex- 
pansion of  the  steam  as  it  works  its 
way  out.  Like  all  multiple  wheel  tur- 
bines, this  makes  them  more  suitable 
for  large  than  smaller  powers.  In 
larger  sizes  the  inner  radius  r  can  be 
made  a  larger  fraction  of  rr 

Then  Wilson  anticipated  the  parallel 
flow  turbine,  with  alternately  fixed  and 
movable  rows  of  blades,  enlarging  their 
area  as  he  reached  the  exhaust  end. 

This  is  shown  in  Fig.  169,  in  which 
fixed  vanes  i,  2,  3  are  fastened  to  the 
outer  casing  H,  and  movable  vanes 
4,  5,  6  are  fastened  to  a  central  shaft  G.  FIG.  168.— Wilson's  Turbine. 

Steam  enters  at  S,  and  expands  through 

the  wheels,  each  successive  wheel  being  of  larger  area  of  wheel  blades  than  the  preceding 
one.     There   we  have  the  whole  of  the  elements  of  the  best  steam  turbines  now  made. 

All  that  was  required  was 
to  design  the  wheels  for  high 
velocity,  and  the  bearings  F 
also  for  a  high  velocity. 

It  will  therefore  be  seen 
from  this  brief  review  of  the 
pioneer  work  in  steam  tur- 
bines that  most  of  the  prin- 
ciples and  designs  are  very 
old,  and  that  the  pioneers 
understood  the  necessities 
of  the  matter,  especially 
Pilbrow  and  his  follower 
FIG.  169.— Wilson's  Parallel  Flow  Turbine.  Wilson.  But  they  could 

not    make    the     machinery 
accurate  and  fine  enough  to  get  the  high  speeds  necessary  for  practical  success. 


PRACTICALLY   DESIGNED   WORKING  TURBINES 

To  Parsons  belongs  the  first  place  in  turbine  making  commercially  and  scientifically 
practical.  His  patents  from  the  first  show  that  he  set  out  to  realise  the  dreams  of  his 
predecessors.  First,  to  design  and  construct  the  wheels  to  work  successfully  at  the 
necessary  high  speeds  ;  and  second,  to  reduce  that  speed  as  far  as  possible  without  loss 
of  efficiency. 

De  Laval  set  out  also  with  the  first  end  in  view,  and  accepted  the  high  speed  as 
unalterable.  Both  succeeded  in  making  practicable  turbines  of  high  efficiency, — the  first 
more  especially  for  large  powers,  and  the  second  more  especially  for  smaller  powers. 


136  Modern   Engines 


There  are  other  practicable  turbines  more  recently  introduced,  the  Rateau  and  two 
or  three  others  worth  describing. 

Matters  in  turbine  progress  stood  much  in  the  stage  at  which  Pilbrow  and  Wilson 
left  them  until  1884,  when  Mr.  Parsons  commenced  to  wrestle  with  the  difficulties. 
Greenock  men  laughed  at  Wilson's  inventions,  and  his  efforts  were  fruitless  to  him,  but 
the  day  came  which  he  had  hoped  for,  when  a  steamship,  the  King  Edward,  touched 
at  Greenock  propelled  by  a  Parsons'  steam  turbine,  a  highly  developed  specimen  of 
Wilson's  type  shown  in  Fig.  169. 

It  had  taken  60  years  to  develop  from  Wilson's  crude  design  to  the  tnrbine  on  that 
ship. 

Mr.  Parsons  laboured  himself  for  fourteen  or  fifteen  years  before  his  great  improve- 
ments were  fully  recognised  by  marine  engineers.  His  patents  had  expired  before  he  began 
to  reap  his  just  rewards.  Fortunately,  his  fundamental  one  was  extended  for  five  years. 

This  slow  progress  of  inventions  in  the  engineering  line  is  a  most  remarkable 
phenomenon.  It  is  difficult  to  find  a  reason  for  it.  We  as  a  manufacturing  nation  go 
on  for  generation  after  generation  using  and  making  old  things  in  the  old  ways  as  long  as 
it  is  ever  possible  to  sell  them.  Some  of  these  things  are  no  doubt  past  improvement  and 
excellent  in  their  way,  but  the  majority  are  subjects  for  improvements.  But  very  slowly 
and  very  reluctantly  are  the  improvements  adopted.  It  is  wonderful ! 

The  internal  combustion  engine  has  the  same  tale  about  it.  It  has  in  one  form  or 
another  been  in  use  for  the  past  fifty  years,  and  only  now  has  it  been  recognised  as  a 
prime  mover  on  a  large  scale  and  its  possibilities  recognised.  The  motor  car  dates  back 
to  the  time  of  James  Watt  and  Murdoch,  yet  it  is  only  now  approaching  the  time  when 
it  will  become  an  important  industry.  The  electric  tramways  in  towns  could  have  been 
laid  down  by  electrical  engineers  in  quite  as  complete  a  system  as  they  are  in  now  in 
the  year  1888,  and  in  quite  a  practicable  manner  in  1884,  yet  it  took  years  and  years  to 
introduce  them,  and  they  only  became  fully  recognised  as  the  best  system  of  rapid  transit 
in  towns  about  10  years  after  their  perfection.  And  then,  of  course,  the  authorities 
began  to  tumble  over  each  other  in  their  eagerness  to  secure  the  advantages  of  the 
"  novel"  system. 

The  same  story  could  be  told  of  the  dynamo  and  the  electric  motor.  The  pioneers 
did  a  lot  of  hard  work  for  nothing  from  1874  till  1886.  And  now  every  engineering  firm 
with  a  vertical  drilling  machine  and  a  turning  lathe  makes  "  the  best  motors  and  dynamos 
in  the  "world"  "  our  own  special  design,"  and  so  on. 

At  this  moment,  when  the  turbine  has  been  recognised  through  Mr.  Parsons'  efforts 
to  be  "the  steam  engine  of  to-day,"  and  we  may  say  "  to-morrow,"  there  is  an  amusing 
keenness  among  engineering  firms  to  enter  as  rival  manufacturers,  and  by  and  by  each 
will  have  a  "special  design  of  his  own,"  even  although  the  difference  between  them  is, 
practically,  only  in  the  colour  of  the  paint.  The  history  of  the  first  adoption  of  the 
Parsons'  steam  turbine  on  mercantile  vessels  is  interestingly  and  concisely  given  in 
Mr.  Archibald  Denny's  remarks  on  Mr.  Parsons'  paper  on  "Marine  Steam  Turbines," 
before  the  Institute  of  Engineers  and  Shipbuilders  in  Scotland,  igth  February  1901. 
As  a  matter  of  history  it  is  worth  recording  : — 

"This  was  not  the  first  time  that  he  had  heard  Mr.  Parsons  lecture  on  this  subject: 
he  heard  him  read  a  paper  to  the  Institution  of  Naval  Architects  about  three  years  ago, 
and  naturally  he  was  impressed  with  the  advantages  of  the  turbine.  Curiously  enough, 
his  firm  had  used  one  for  driving  the  dynamo  on  board  the  s.s.  Duchess  of  Hamilton, 
built  some  years  ago,  and  it  worked  exceedingly  well.  When  he  heard  Mr.  Parsons 
read  his  paper  before  the  Institution  of  Naval  Architects  he  was  fired  with  the  ambition 
to  work  with  him  for  the  success  of  the  turbine.  Several  months  ago  his  firm  got  in 
touch  with  Mr.  Parsons,  and  they  made  up  their  minds  that  if  possible  they  would  jointly 
get  a  turbine  vessel  built  for  the  mercantile  marine.  They  naturally  approached  the 
railway  companies  in  the  first  instance,  but  they  affected  a  terrible  amount  of  modesty, 


Parsons'  Turbines  137 

and  each  company  was  anxious  that  somebody  else  should  make  the  first  experiment. 
So  the  matter  was  hung  up,  and  he  was  beginning  to  despair  of  success  when  Mr.  John 
Williamson  came  forward  and  lent  them  his  aid.  Mr.  Parsons,  Mr.  Williamson,  and 
his  firm,  having  laid  their  heads  together,  resolved  to  build  a  mercantile  turbine  vessel, 
and  he  felt  it  was  very  gratifying  indeed  that  the  Clyde  had  been  favoured  in  being  the 
pioneer  in  this  enterprise.  It  was  gratifying  to  think  that  this  was  taking  place  during 
the  era  of  the  Exhibition,  when  many  people  would  be  able  to  see  the  advantages  of 
this  system." 

The  attitude  of  the  railway  companies  referred  to  is  the  common  one. 

To  proceed  with  the  turbine  construction,  we  will  take  the  first  patent  of  Mr. 
Parsons,  as  that  marks  an  epoch  in  the  art  of  turbine  making. 

This  invention  has  reference  to  motors  of  the  turbine  type  ;  that  is  to  say,  to 
motors  in  which  the  actuating  fluid  operates  between  fixed  and  moving  vanes  or  blades. 
When  elastic  fluids  such  as  gas  and  steam  are  used  in  a  motor  of  this  description,  it  is 
necessary  for  economical  working  that  the  peripheral  speed  of  the  motor  should  be  nearly 
as  great  as  the  velocity  of  the  gas  or  steam,  due  to  its  effluent  pressure,  a  speed  which, 
except  with  very  low  pressure,  is  practically  impossible. 

According  to  this  invention,  to  obtain  a  low  effluent  or  terminal  pressure  while 
using  a  comparatively  high  initial  pressure,  a  compound  motor,  or  a  combination  of 
motors,  are  so  arranged  that  the  same  actuating  fluid  operates  therein  in  a  successive 
manner,  undergoing  expansion  and  falling  in  pressure  in  each,  until  it  leaves  the  last 
at  a  velocity  not  greatly  above  that  which  is  practically  attainable  by  the  motor  itself, 
although  greatly  above  that  practicable  with  a  motor  having  oscillating  or  recipro- 
cating parts.  By  this  arrangement  each  motor,  or  successive  portion  of  the  compound 
motor,  utilises  a  portion  of  the  energy  of  the  fluid,  and  thus,  instead  of  the  greater  part 
being  wasted  as  heretofore,  it  is  successively  drawn  upon  until  a  comparatively  high 
efficiency  is  obtained. 

The  motors,  or  successive  portions  of  the  compound  motor,  may  be  arranged 
either  upon  one  common  shaft  or  upon  different  shafts.  In  the  former  case  the  first 
will  deliver  directly  into  the  second,  and  the  second  into  the  third,  and  so  on,  the  moving 
vanes  of  the  second  (say)  rotating  between  its  own  fixed  vanes,  and  those  of  the  third, 
and  similarly  for  the  others  ;  the  space  for  the  actuating  fluid  increasing  either  con- 
tinuously, or  step  by  step. 

This  increase  may  be  conveniently  gained  either  by  an  increased  area,  or  by  an 
increased  pitch  of  the  blades,  or  by  an  increased  area  and  pitch  combined. 

The  successive  motors,  or  portions  of  a  compound  motor,  are  arranged  in  such  wise 
as  to  form  an  approximately  cylindrical  figure,  the  whole  being  mounted  by  preference 
upon  one  and  the  same  shaft ;  the  first  delivering  into  the  second,  the  second  into  the 
third,  and  so  on. 

Each  motor  or  portion  comprises  a  set  of  fixed  and  a  set  of  moving  vanes,  the 
direction  of  motion  of  the  actuating  fluid  being  generally  parallel,  or  approximately  so, 
to  the  axis  of  the  combined  motors. 

Conveniently,  each  set  of  moving  blades  can  be  formed  out  of  the  solid  metal  on 
the  circumference  of  a  brass  or  steel  disc,  the  blades  extending  only  about  one-third  of 
the  breadth  of  the  disc,  and  the  blank  portion  forming  part  of  the  moving  cylinder 
beyond  which  the  blades  extend. 

Likewise,  the  fixed  blades  can  be  formed  by  cutting  each  row  internally  on  a  ring 
which  is  afterwards  cut  diametrically  into  two  parts,  one  to  be  joined  to  the  top  half  of 
the  casing,  which  is  divided  into  two  parts  by  a  longitudinal  joint,  and  the  other  into  the 
lower  portion  of  the  casing.  When  all  the  parts  are  put  together  the  fixed  portion 
forms  a  hollow  cylinder  with  projecting  rings  of  blades,  and  the  moving  portion  a  solid 
(or  hollow)  cylinder,  also  with  projecting  rings  of  blades. 

To  balance  the  end  pressure  upon  the  cylinder,  two  similar  sets  of  rotary  parts  are 


138  Modern  Engines 


mounted  upon  one  shaft,  one  set  being"  placed  at  each  side  of  the  inlet  for  actuating1  fluid, 
in  such  a  way  that  the  entering  stream  shall  divide  right  and  left,  and  the  exhaust  take 
place  at  both  ends.  Any  end  pressure  not  thus  balanced,  or  due  to  external  causes,  can 
if  desired  be  balanced  by  pressure  of  the  exhaust  fluid  acting  between  the  end  of  the 
moving  cylinder  and  a  collar  of  smaller  diameter  than  the  cylinder.  Thus,  should  the 
cylinder  be  displaced  endwise  in  either  direction,  the  exhaust  will  be  checked  at  that  end, 
and  in  this  way  a  compensation  will  be  automatically  effected. 

As  the  speed  of  the  motor  will  be  necessarily  and  designedly  high,  and  perfect 
balancing  of  the  moving  parts  would  not  be  practicable,  the  bearings  are  given  a  certain 
very  small  amount  of  elasticity  or  play,  combined  with  a  frictional  resistance  to  their 
motion.  Thus  the  cylinder  will  be  enabled  to  rotate  around  its  centre  of  gravity,  instead 
of  its  geometrical  centre,  if  the  two  be  nearly  coincident,  and  the  vibration  to  which  it 
may  be  subject  will  thereby  be  damped  or  modified. 

The  lubrication  is  effected  by  forcing  lubricant  to  the  parts  to  be  lubricated,  and 
for  this  purpose  a  pump  can  be  employed.  Conveniently  it  may  be  a  centrifugal  pump, 
of  the  type  in  which  the  fan  is  constructed  like  a  screw  propeller  mounted  on  the  end  of 
the  shaft.  From  this  pump  the  oil  will  be  taken  to  the  bearings  as  required,  with  a 
constant  circulation.  The  oil  can  also  be  used  as  a  carrier  of  heat,  to  reduce  the  tem- 
perature of  the  parts  liable  to  grow  hot.  If  the  pump  be  of  a  kind  that  will  not  lift,  a 
suction  fan  mounted  on  the  motor  shaft  may  be  used  to  raise  the  oil  on  the  suction  side. 
This  fan  may  also  be  employed  to  govern  the  supply  of  actuating  fluid,  by  causing 
variations  of  pressure,  according  to  the  speed  at  which  it  is  driven,  on  a  diaphragm 
or  piston  in  connection  with  the  throttle  or  supply  valve.  The  speed  of  the  motor  may 
be  regulated  by  an  adjustable  spring  acting  against  this  varying  pressure,  or  by  the 
admission  of  air  through  a  graduated  regulating  tap  into  the  exhausting  side  of  the  fan. 

To  prevent  leakage  past  the  shaft  at  the  end  covers  of  the  casing,  which,  when 
steam  is  the  actuating  fluid,  would  be  inconvenient,  annular  recesses  are  formed  in  the 
covers  around  the  shaft  ends,  and  place  these  recesses  in  communication  with  a  pipe  in 
which  a  partial  vacuum  is  maintained  by  suitable  means  such  as  a  steam  jet.  Any 
steam  which  enters  the  recesses  will  thus  be  drawn  away  without  apparent  leakage. 

Motors,  according  to  this  invention,  are  applicable  to  a  variety  of  purposes,  and  if 
such  an  apparatus  be  driven  it  becomes  a  pump,  and  can  be  used  for  actuating  a  fluid 
column,  or  producing  pressure  in  a  fluid.  Such  a  fluid  pressure  producer  can  be  com- 
bined with  a  multiple  motor  according  to  this  invention,  so  that  the  necessary  motive 
power  to  drive  the  motor  for  any  required  purpose  may  be  obtained  from  fuel  or  com- 
bustible gases  of  any  kind.  For  this  purpose  the  pressure  producer  is  employed  to  force 
air  or  combustible  gases  into  a  close  furnace  of  any  suitable  kind  such  as  used  for  caloric 
engines,  into  which  furnace  there  may  or  may  not  be  introduced  other  fuel  (liquid  or  solid). 
From  the  furnace  the  products  of  combustion  can  be  led,  in  a  heated  state,  to  the  multiple 
motor,  which  they  will  actuate.  Conveniently  the  pressure  producer  and  multiple  motor 
can  be  mounted  on  the  same  shaft,  the  former  to  be  driven  by  the  latter ;  but  the 
inventor  does  not  confine  himself  to  this  arrangement  of  parts. 

The  blades  should  be  of  material  that  will  withstand  high  temperatures,  or  water  or 
other  fluid  may  be  employed  to  cool  the  blades.  This  may  be  done  by  providing,  in  the 
cylinders  that  carry  the  blades,  channels  or  passages  for  the  circulation  of  the  cooling 
fluid,  which,  in  the  case  of  the  rotary  cylinder,  may  be  supplied  through  a  passage  or 
passages  in  the  shaft  carrying  the  cylinders. 

It  will  be  observed  at  once  that  the  inventor  tackled  the  points  requiring  improve- 
ment. 

First,  to  reduce  the  velocity  of  steam  flow  as  far  as  possible,  so  that  the  turbine 
speed  would  approach  in  peripheral  velocity  at  least  half  the  velocity  of  the  steam.  This 
he  does,  as  had  been  done  before,  by  forcing  the  steam  to  pass  in  series  through  many 
wheels.  The  more  it  is  baffled  on  its  way  to  the  exit  by  deviating  its  course  by  wheel 


Parsons'  Turbines 


139 


blades,  the  slower  is  its  progress,  and  the  more  of  its  energy  is  exhausted  by  giving-  it 
away  to  the  wheels — that  is  the  whole  philosophy  of  the  wheels  in  series. 

To  balance  the  steam  pressure  the  turbine  was  made  double  ended,  steam  entering 
at  the  middle  and  balancing.  This  is  still  a  good  plan  for  pressure  turbines  ;  better,  in 
the  author's  opinion,  than  the  dummy  plan  later  adopted.  Then  he  proceeds  to  the  real 
problems  to  be  solved.  He  knows  that  a  perfect  balancing  of  the  rotating  parts  is 
mechanically  impossible;  he  therefore  devises  bearings  with  some  elasticity  or  play  in 
order  to  allow  the  "wheels  to  settle,"  that  is,  to  rotate  round  their  centre  of  gravity. 


FIG.  170. — Parsons'  First  Turbine. 

The  penultimate  paragraph  in  this  patent  is  of  interest ;  it  shows  that  the  turbine 
is  reversible,  and  will  act  as  a  pump  if  driven  by  power.  This,  we  have  seen  in  Fig. 
145,  has  been  accomplished,  and  then  he  foreshadows  a  hot  gas  turbine  in  which  the 
air  is  to  be  forced  into  a  closed  furnace  supplied  by  fuel  ;  the  products  of  combustion 
are  then  to  be  led  into  the  turbine  which  drives  the  pump,  and  so  drive  the  turbine. 
This  scheme  has  never  been  put  into  practice,  so  far  as  can  be  ascertained,  and  it  was 
dropped  out  of  the  specification.  It  contains,  however,  the  germ  of  the  gas  turbine  or 
internal  combustion  turbine. 

Fig.  1 70  is  a  longitudinal  horizontal  cross  section  of  the  turbine,  with  two  sets  of  wheels 


FIG.  171. — Parsons'  Turbine,  with  Expanding  Wheels. 

right  and  left  of  the  steam  inlet  Sr  The  b,  bv  62  are  the  movable  blades,  and  thef,fvfz 
the  fixed  blades.  These  blades  were  originally  cut  out  of  the  solid  brass  rings,  and 
were  merely  flat  blades  at  an  angle  of  45°  with  the  axis. 

In  this  form  the  diameter  of  the  wheels  are  all  alike,  and  expansion  is  obtained  by 
making  the  blades  deeper  radially  as  they  near  the  exhaust  end. 

Later  on  the  plan  shown  in  Fig.  171  was  adopted,  in  which  not  only  are  the  blades 
increased  in  depth  radially,  but  they  are  also  increased  in  diameter  in  3  sections,  making 
it,  as  it  were,  triple  expansion.  And  in  order  to  preserve  the  balance  of  steam  pressure, 


140 


Modern   Engines 


steam  passages  are  formed  in  the  casing  connecting  the  annular  space  between  each  set 

and  the  exhaust  ends,  so  that  the  pressures  are  all  equalised. 

For  giving   to   the  bearings   a  certain   very  small   amount  of  elasticity  or   play, 

combined  with  a  frictional  resistance  to  their  motion,  in  the  arrangement  of  motor  now 

under  description,  this  is  done  by  constructing  the  bearings  of  shaft  s  in  the  manner 

represented  in  Fig.  172. 

I  is  a  light  bush,  outside  of  which  are  placed  metal  rings  or  washers  KK1.     The 

alternate  washers   K  are  slightly  larger  than  the  washers   K1,  so  that  the  alternate 

washers  K  fit  the  casing  but  not  the  bush,  and  the  washers  K1  fit  the  central  bush  but 

not  the  casing.  L  is  a  spiral  spring,  and 
M  is  a  nut.  By  these  the  rings  or  washers 
KK1  are  pressed  tightly  together.  Thus  the 
bush  is  capable  of  a  slight  lateral  move- 
ment, but  this  movement  is  resisted  and 
controlled  by  the  rings  or  washers  and  their 
mutual  friction.  The  amount  of  liberty  given 
to  the  rings  or  washers  may  be,  say,  y^ 
part  of  an  inch  diametrically,  but  it  may  be 
more  or  less  according  to  circumstances  as 
may  be  found  desirable  in  practice.  It  will 
be  evident  that  any  movement  of  the  central 


FIG.  172. — Turbine  "Ring"  Bearing. 


bush  in  a  lateral  sense  will  be  opposed  by  the  frictional  resistance  of  the  rings  or 
washers.  In  lieu  of,  or  in  conjunction  with,  rings  or  washers,  such  as  KK1  with  spiral 
spring  and  nut,  a  steel  cage  such  as  illustrated  in  Fig.  173  may,  in  some  cases,  be  used  to 
surround  the  bush  i  for  the  purpose  of  maintaining  it  in  place  whilst  admitting  of  very 
slight  lateral  play  or  elasticity.  This  cage  n  as  represented  is  formed  with  longitudinal 
slots  n1,  so  that  the  intervening  parts  n2  will  act  as  springs,  pressing  tightly  against  the 
central  projecting  part  z1  of  the  bush,  thus  resisting  any  lateral  movement  principally  by 
elasticity  of  the  cage.  To  obtain  very  quiet  running,  however,  it  is  preferable  to  use  a 
combination  of  the  two  arrangements,  constructed  by  placing  a  steel  cage  such  as  n  or 
its  equivalent  around  the  washers  KK1  in  order  to  check  the  communication  of  vibrations 
from  the  rings  or  washers  to  the  bearing  itself. 
In  Fig.  170^  are  metal  washers  fitting  easily  on 
shaft  j  to  prevent  leakage  of  steam  past  the 
bushes  ylyl.  oo  are  drain  passages  from  each 
end  of  the  hollow  cylinder.  They  pass  over  the 
top  of  the  motor  and  meet  at  its  centre.  Their 
purpose  is  to  drain  away  any  of  the  steam  that 
may  escape  between  the  shaft  ^  and  bushes  yl 
fixed  in  the  motor.  This  is  effected  by  an  arrange- 
ment shown  clearly  in  Fig.  174.  Where  the  drain 
passages  oo  meet,  there  is  provided  an  ejector  or  steam  nozzle  p,  to  which  steam  is 
admitted  from  the  supply  branch.  This  steam  flows  into  an  exhaust  pipe  g,  and  the 
partial  vacuum  thus  created  causes  the  steam  to  flow  from  the  passages  oo  and  to  pass 
away  through  the  drain  pipe  q. 

His  next  form  of  turbine  is  shown  in  Fig.  175,  a  series  of  radial  flow  turbines  ending 
in  a  large  disc  series  of  outward  flow  turbines  like  Wilson's  (Fig.  168).  The  construction 
is  thus  explained  : — 

It  consists  of  a  new  arrangement  of  balance  piston  designed  to  minimise  leakage  ; 
a  method  of  bolting  the  rings  or  discs  together  on  the  turbine  spindle  ;  the  use  of  a 
large  disc  with  blades  to  expand  the  steam  to  a  very  low  pressure  when  a  condenser  is 
adopted,  and  an  application  of  the  principle  of  the  relay  to  solenoid  electrical  governors 
for  steam  turbines. 


FIG.  173. — Turbine  "Cage"  Bearing. 


Parsons'  Turbines 


141 


Fig.  175  is  a  sectional  elevation  of  this  turbine  with  balance  piston  shown  thereon, 
also  illustrating  the  method  of  bolting  the  rings  or  discs  together  on  the  turbine  spindle, 
and  use  of  a  large  disc  with  blades  to  expand  the  steam  to  a  low 
pressure  when  a  condenser  is  adopted. 

Fig.  A  shows  the  balance  piston  E  on  a  larger  scale  in  part  section. 
Another  part  of  the  invention  relates  to  fastening  the  discs  on  the 
turbine  spindle,  and  for  this  purpose  the  spindle  A  has  a  collar  cl  at  one 
end,  and  into  this  collar  cl  pass  long  bolts  or  studs  cc,  which  pass 
through  holes  in  the  turbine  discs  as  B,  B1,  B2,  B3,  B4,  B5,  and  B6,  and 
through  holes  in  the  balance  piston  E.  The  discs  are  thus  screwed  up 
and  are  firmly  held  on  the  spindle,  together  with  the  balance  piston. 

The  invention  also  relates  to  turbines  intended  for  great  expansion 
and  exhausting  into  a  condenser.  In  these  turbines  a  large  disc  as  Bti 
(Fig.  175)  is  fixed  on  one  or  preferably  both  its  faces,  and  the  steam, 
after  passing  through  a  sufficient  number  of  turbine  pairs  to  reduce  its  for74 
pressure  to  atmosphere,  or  nearly  so,  passes  by  one  or  both  faces  of  ste; 
the  large  disc,  and  by  its  impact  between  fixed  and  moving  blades,  gives 
up  its  energy,  and  passes  to  the  condenser,  being  first  reduced  in  pressure  until  very 
little  energy  is  left  to  be  carried  to  the  vacuum.  The  large  disc  is  arranged  as  an  out- 
ward flow  radial  turbine,  and  the  passage  communicating  with  the  condenser  surrounds 
it  so  that  the  steam  passes  on  one  or  both  sides  of  the  disc  from 
A  ^<<<^x  tne  turkine  through  the  fixed  and  moving  blades. 

This  same  outward  flow  disc  turbine  is  shown  at  K  in  Fig. 
158,  already  referred  to  in  conjunction  with  his  Hero  type  of 
turbine. 

Mr.  Parsons  also  patented  an  inward  flow  steam  turbine,  much 
41  «i  et^L"  l*ke  a  series  of  vortex  wheels  as  used  in  Professor  James  Thomson's 


FlG.  175. — Parsons'  Radial  Flow  Compound  Turbine. 

vortex  turbine.  It  is  shown  in  Fig.  176,  a  longitudinal  section  and  a  part  cross  section. 
In  steam  turbines  of  the  kind  at  present  in  use  the  steam  is  caused  to  perform 
work  by  alternate  impact  upon  and  reaction  from  a  large  number  of  rotating  vanes  or 
blades,  and  the  steam  is  suitably  directed  or  guided  by  fixed  vanes  or  blades  of  con- 
venient shape  and  disposition.  In  such  motors  it  is  impossible  to  obtain  the  maximum 


Modern  Engines 


142 

economy  in  the  consumption  of  steam  unless  the  clearances  between  the  rotating-  blades 
and  the  enclosing-  conical,  disc,  or  cylindrical  surfaces  and  the  fixed  blades  and  rotating 
surface  is  very  small.  This  necessitates  considerable  delicacy  in  the  adjustment  and 
accuracy  in  the  construction  of  the  motors,  and  renders  it  difficult  to  keep  them  in  such 
condition  as  to  bearing-  surfaces  that  the  best  economy  may  be  obtained  in  practical 
work  through  a  long-  term  of  years. 

As  applied  to  turbines  of  the  inward  flow  type,  a  series  of  inward  flow  turbine 
wheels,  upon  one  rotating  shaft  or  spindle  and  enclosed  in  one  cylinder  or  case  contain- 
ing- the  directing  vanes  or  guide  blades,  in  such  manner  that  steam  entering  the  first  of 
the  series  passes  successively  through  each  before  being  discharged  into  the  atmosphere 
or  condenser.  The  turbine  wheels  consist  of  metallic  discs  combined  with  bushes,  which 
are  slipped  upon  the  shaft  or  spindle,  and  firmly  keyed  or  fixed  to  it  in  any  other 
convenient  manner.  Each  disc  carries  upon  a  face  or  faces,  or  upon  an  edge  or  edges, 
one  or  more  series  of  blades,  of  suitable  shape  and  curvature,  in  which  the  general 
direction  is  that  of  radiation  from  the  centre  towards  the  circumference.  The  enclosing 
case  or  cylinder,  preferably  made  in  halves,  carries  ring  projections  and  guide  blades  or 
vanes,  and  the  ring  projections  are  arranged  so  as  to  form  a  series  of  chambers  in  which 
the  turbine  wheels  rotate.  Each  wheel  chamber  may  for  facility  of  construction  consist 


FIG.  176. — Parsons'  Turbine  with  Fixed  and  Movable  Vanes. 

of  two  rings  projecting  from  the  interior  of  the  cylinder  or  case  to  enclose  a  wheel  in  which 
the  steam  is  caused  to  pass  outwards  by  the  first  partition  or  ring,  and  then  over  a 
space  between  it  and  the  case  to  the  annular  space  behind  the  fixed  guide  blades  or 
vanes,  which  are  disposed  around  the  circumference  of  the  wheel  and  direct  the  flow  of 
steam  tangentially  upon  the  blades  or  vanes  of  the  rotating  wheel.  After  passing  the 
rotating  wheel  vanes  or  blades,  the  steam  flows  towards  the  centre  and  is  brought 
almost  to  rest,  thus  giving  up  the  greater  part  of  its  energy  of  motion  to  the  wheel. 
The  steam  then  flows  through  an  annular  space  around  the  rotating  bush  or  spindle,  and 
is  directed  outwards  by  the  next  projecting  ring  partition  to  the  fixed  vanes  or  guide 
plates  of  the  next  wheel  in  the  series,  there  to  experience  a  further  fall  in  pressure  and  a 
further  expansion,  and  so  on  until  the  desired  total  expansion  is  accomplished.  In 
order  to  prevent  leakage  from  any  wheel  chamber  to  the  next,  whereby  a  portion  of 
steam  would  be  allowed  to  pass  without  flowing  through  the  guide  blades,  the  first 
partition  ring  of  each  chamber  is  placed  close  to  the  rotating  bush  carrying  the  wheel  or 
close  to  the  spindle  itself,  and  grooves  or  a  series  of  grooves  are  cut  in  the  portions  of 
bush  or  spindle,  and  ring,  opposing  each  other,  which  grooves  and  projections  may 
alternately  project  into  each  part  without  touching  or  nearly  touching  laterally  or 
longitudinally.  In  order  to  reduce  leakage  past  the  faces  of  the  rotating  vanes  or 
blades  moving  near  the  enclosing  partition,  a  ring  is  attached  to  the  lower  edge  of  those 
vanes  or  blades,  or  otherwise  shroud  the  blades  which  project  under  the  fixed  partition 


Parsons'  Turbines 


ring,  and  by  so  bafflingf  the  steam  diminish  leakage.  At  all  surfaces  where  leakage  is 
likely  to  occur,  which  surfaces,  of  course,  cannot  be  packed  or  rotated  in  close  contact, 
alternate  recesses  and  projections,  or  recesses  only,  are  cut  to  give  the  steam  a  tortuous 
path  and  reduce  leakage.  The  fixed  guide  blades  form  part  of  one  of  the  partition  rings. 

The  series  of  turbine  wheels  may  be  mounted  on  a  conical,  stepped,  or  cylindrical 
spindle,  as  circumstances  may  require,  and  the  successive  wheels  may  be  of  the  same 
diameter  or  different  diameters,  generally  increasing,  as  determined  by  the  desired 
amount  of  expansion,  the  number  of,  and  discharge  area  at,  the  guide  blade  orifices  ; 
and  the  number  and  configuration  of  moving  blades  is  also  varied  to  suit  various  condi- 
tions of  steam  pressure  and  expansion.  The  vibration  caused  by  slight  want  of  balance 
by  means  of  the  following  contrivance  is  damped  : — 

The  spindle  ends  run  in  a  bush  fixed  into  another  bush  with  slight  treedom  of  fit, 
and  this  into  another,  and  so  on,  giving  a  number  of  concentric  bushes  having  slight 
play  the  one  within  the  other.  The  ends  of  these  bushes  fit  into  a  case  with  some  nicety 


FIG.  177. — Single-Ended  Parsons'  Turbine. 

of  end  fit,  but  this  is  not  always  necessary,  and  fill  the  case  with  oil,  the  outer  bush 
being  fixed  securely.  Any  vibrating  movement  is  now  checked  or  damped  by  the 
forcing  out  of  oil  between  the  bushes  and  the  ends  and  circumferentially  around  the 
bushes,  so  that  although  a  slight  movement  is  possible,  yet  it  is  resisted  in  whatever 
direction  it  may  tend  to  move.  Spring  supported  bearings  may  be  used,  and  hydraulic 
resistance  of  other  kinds  may  be  interposed  such  as  that  due  to  a  small  cylinder  or  ram. 
The  bush  in  which  the  spindle  runs  is  packed  with  segments  of  a  thin  cylinder  or  tube, 
which  segments  may  be  of  greater  or  less  curvature  than  the  outer  surface  of  the  bush, 
and  so  cause  bearing  of  the  segment  ends  upon  the  exterior  of  the  bush  or  the  interior 
of  the  bored  surface  holding  it.  This  arrangement  gives  a  spring  or  elastic  movement, 
and  when  oil  or  other  liquid  is  present  the  hydraulic  resistance  already  hereinbefore 
described  is  also  brought  into  play. 

In  order  to  prevent  leakage  of  the  steam  past  the  spindle,  a  series  of  grooves  or 
projecting  collars  are  fitted  upon  the  spindle  fitting  into  or  working  easily  in  a  similar 
series  of  grooves  in  an  end  bush,  and  by  using  a  sufficient  number  leakage  may  be 


Modern   Engines 


reduced  to  any  desired  extent.  Instead  of  this,  metallic  packing-  rings  may  be  used. 
When  the  steam  turbine  is  arranged  so  that  there  is  end  thrust  in  any  direction,  and  to 
obviate  end  wear  for  an  inevitable  small  end  thrust,  that  end  thrust  is  taken  in  a  thrust 
block  of  construction  similar  to  those  used  in  marine  engines  ;  but  in  order  to  secure 
that  each  thrust  collar  shall  take  its  share  of  the  pressure,  and  so  produce  a  uniform 
slight  pressure  over  a  considerable  surface,  which  uniformity  is  necessary  to  run  cool  at 
high  velocities,  the  collars  or  flanges  have  a  slight  elastic  movement,  bringing  them  to 
bear  with  a  predetermined  pressure  upon  their  respective  collars  on  the  turbine  spindle. 
Thus  they  distribute  the  pressure  upon  the  surfaces  accurately,  and  make  certain  that 
no  one  surface  is  subject  to  undue  pressure. 

A  standard  type  was  at  last  arrived  at,  as  shown  in  Fig.  177.  This  turbine  is  single 
ended,  and  balanced  by  dummy  pistons  instead  of  by  another  turbine. 

It  was  long  known  that  a  piston  well  fitted,  but  yet  smaller  in  bore  than  a  cylinder 
in  which  it  can  move  freely,  offers  a  considerable  resistance 
to  the  leakage  of  fluids  ;  and  if  the  piston  is  long  and 
grooved  with  many  grooves  the  resistance  to  leakage  is 
very  great.  An  air  pump  was  used  at  one  time  largely 
working  on  this  principle  ;  it  is  shown  partly  in  Fig.  178, 
which  shows  the  barrel  and  grooved  piston.  The  piston 
does  not  touch,  the  barrel  being  y^^  of  an  inch  clear  ;  it 
requires  no  oiling,  and  has  no  friction.  Arc  lamp  dash 
pots  are  made  on  the  same  principle.  In  later  steam 
turbines  this  principle  has  also  been  adopted  instead  of 
packing.  Mr.  Parsons  carries  it  further  when  the  piston 
is  to  rotate  instead  of  reciprocate  ;  he  grooves  the  cylinder 
to  fit  the  piston,  thus  adding  still  further  to  the  resistance 
to  leakage.  The  three  dummy  pistons  are  thus  fitted  in  the 
turbine  case,  and  very  little  leakage  occurs,  while  they 
balance  the  steam  pressures. 

This  system  of  packing  steam  tight  will  be  again 
referred  to  under  Cylinder  and  Piston  Engines.  With 
modern  machine  tools  it  is  possible  to  fix  piston  rods  and 
pistons  without  the  old-fashioned  packings,  spring  rings, 
and  other  nostrums.  Deluel's  old  air  pump  contained 
this  valuable  principle  in  its  construction,  hence  it  is 
worthy  of  reference  again  to  it.  With  the  construction  of 
this  type  of  turbine  Mr.  Parsons  arrived  at  a  permanent 
design  for  land  engines. 
In  vessels  of  the  mercantile  marine  of  moderate  fast  speed  it  is  of  more  importance 
to  obtain  economy  in  coal  consumption  than  to  reduce  the  weight  of  the  engines  and 
condensers  to  their  lowest  limits,  as  is  usually  done  in  torpedo-boat  destroyers,  where 
the  boilers  are  extremely  light  and  heavily  pressed,  and  the  highest  possible  speed  is  the 
first  consideration. 

For  the  mercantile  marine,  therefore,  it  becomes  desirable  to  design  the  turbines 
for  the  greatest  possible  economy  in  steam,  consequently  the  ratio  of  expansion  extends 
over  nearly  the  whole  range  between  the  boiler  pressure  and  that  in  the  condenser  ;  the 
condensers  are  also  made  of  ample  size  so  as  to  maintain  a  good  vacuum,  and  an 
efficient  feed-heating  arrangement  is  provided  to  warm  and  heat  the  feed. 

The  marine  steam  turbine  will  be  found  to  be  superior  or  at  least  equal  in  economy 
of  coal  to  the  reciprocating  engine  when  placed  in  fast  vessels  of  the  mercantile  marine  ; 
but  it  may  be  asked,  What  will  be  the  economy  of  the  turbines  when,  as  in  the  case  of 
yachts  and  almost  all  war  vessels,  much  steaming  is  done  at  from  one-eighth  to  one-tenth 
power,  the  full  power  being  only  occasionally  used  ?  The  answer  is  a  simple  one.  At 


FlG.  178.— Deluel's  Piston. 


PLATE  VI.— SMALL  DE  LAVAL  TURBINE  MOTOR. 


Marine  Steam  Turbines  145 

cruising-  speeds  the  revolutions  of  the  turbines  fall  well  within  the  limits  of  speed  of 
small  reciprocating  engines,  and  such  small  engines  are  then  directly  coupled  to  the 
main  turbines,  and  work  in  conjunction  with  them,  these  small  triple  -  expansion 
reciprocating  engines  taking  the  steam  directly  from  the  boilers  and  expanding  it  down 
to  about  atmospheric  pressure  ;  it  then  passes  to  the  high  pressure  turbine,  and  thence 
through  the  low  pressure  turbines  to  the  condensers. 

It  should,  however,  be  added  that  the  turbines  alone  have  their  full  measure  of 
economy  from  half  to  full  power,  and  even  at  one-quarter  full  power  the  economy 
is  good.  It  is  only  when  the  cruising  speed  falls  to  nearly  one-half  the  full  speed, 
and  the  horse-power  one-eighth  of  full  power,  that  the  economy  of  the  turbines  requires 
some  assistance,  and  such  additions  are  only  necessary  in  vessels  such  as  war  vessels 
and  some  yachts,  where  much  running  is  done  at  these  very  low  speeds.  They  are  quite 
unnecessary  in  passenger  vessels  and  liners. 

.  The  arrangement  of  turbine  machinery  for  an  Atlantic  liner  of  20,000  to  30,000 
indicated  horse-power  presents  no  features  of  novelty  over  the  preceding  designs,  but 
its  simplicity  of  construction,  as  compared  with  the  present  usual  reciprocating  engine, 
is  more  apparent  than  in  smaller  vessels. 

The  adaptation  of  steam  turbines  to  marine  propulsion  required  two  efforts.  The 
screw  propellers  in  use  are  all  slow  speed,  the  turbines  of  high  speed  ;  hence  propellers 
have  had  to  be  designed  to  bring  up  their  speed  to  the  lowest  possible  speed  of  the 
turbines,  and  the  turbines  had  to  be  designed  to  drive  at  the  highest  speed  permissible 
by  the  screw  propeller. 

The  next  improvements  relate  to  marine  engines.  The  steam  turbine  is  not  an 
engine  in  which  the  motion  can  be  reversed  readily,  and  in  locomotive  work  and  marine 
propulsion  reversing  is  a  necessity,  while  in  stationary  engines  it  is  seldom  necessary 
except  in  the  case  of  mining  winding  engines.  Pilbrow  proposed  to  use  turbines  on 
locomotives,  but  as  yet  no  locomotive  has  been  successfully  worked  by  them.  And  it  is 
curious  also  that  the  internal  combustion  engines  are  not  yet  made  reversing.  In  marine 
steam  turbines  Mr.  Parsons  has  met  the  difficulty  very  well  by  employing  separate 
reversing  turbines  of  smaller  power  than  the  main  turbines.  Mr.  Parsons'  views  on 
the  marine  steam  turbine  were  given  in  his  paper  already  referred  to. 

The  most  important  field  for  the  steam  turbine  is  undoubtedly  in  the  propulsion 
of  ships.  The  large  and  increasing  amount  of  horse-power,  and  the  greater  size  and 
speed  of  the  modern  engines,  tend  towards  some  form  which  shall  be  light,  capable 
of  perfect  balancing,  and  economical  in  steam.  The  marine  engine  of  the  piston  type 
does  not  entirely  fulfil  all  these  requirements. 

Though  for  obvious  reasons  up  till  the  present  time  turbines  have  only  been  fitted 
in  vessels  designed  for  phenomenal  speeds,  yet  it  must  not  on  this  account  be  assumed 
that  they  are  only  applicable  to  such  vessels.  The  two  conditions  of  suitability  are  that 
the  vessel  shall  have  a  moderately  fast  speed  and  be  of  moderately  large  size.  For  slow 
vessels  of  moderate  and  small  size  the  conditions  for  turbine  machinery  are  not  at  the 
present  time  so  advantageous. 

This  will  appear  clear  when  we  consider  that  the  turbine  machinery  is  actuated  by 
the  momentum  of  the  steam,  and  that  the  rows  of  blades  must  be  sufficiently  numerous, 
and  must  move  at  a  sufficiently  high  velocity  to  secure  a  good  efficiency  from  the  steam. 
The  class  of  vessels  that  are  most  suitable  for  the  application  of  turbine  machinery  are 
the  following  :  Pleasure  steamers,  passenger  and  cross-channel  steamers,  liners  (including 
Atlantic  liners  of  the  largest  size),  also  all  fast  war  vessels,  such  as  torpedo-boats, 
destroyers,  cruisers  of  all  sizes,  protected  cruisers,  and  all  battleships  of  the  usual 
speeds. 

Now,  considering  that  turbines  are  not  reversible  in  motion,  and  that  they  are  best 
driven  at  high  velocities  far  beyond  the  permissible  speed  of  a  screw  propeller,  it  seems  to 
my  mind  that  Mr.  Parsons  might  consider  an  intermediate  transmission  gearing  between 
VOL.  i. — 10 


146  Modern  Engines 


the  turbine  and  the  propeller.  The  introduction  of  an  auxiliary  reciprocating  engine 
as  proposed,  along  with  a  reversing  pair  of  turbines  and  the  special  screw  propellers, 
somewhat  detracts  from  the  advantages  of  the  simplicity  of  turbines  ;  and  if  all  that 
extra  machinery  could  be  replaced  by  some  transmission  of  power  system  flexible  enough 
for  speed  variations  and  reversing,  some  considerable  advantages  might  accrue.  In  my 
own  view,  there  are  two  systems  which  might  be  tried :  first,  an  electric  transmission. 
Let  the  turbines  run  dynamos  of  small  size  at  high  speed,  and  let  the  current  operate 
motors  on  the  propeller  shaft  at  moderate  speeds.  With  modern  electric  machinery 
this  should  present  no  difficulties  ;  even  in  large  ships  the  control  would  be  perfect. 

The  other  system  is  a  hydraulic  one,  in  which  the  turbines  would  pump  water  to 
a  pressure  to  work  by  water  jet  propellers.  Properly  designed,  this  would  also  be 
feasible,  at  any  rate,  for  small  craft.  In  this  way  the  turbine  speed  could  be  adapted 
to  the  best  speed  for  economy. 

The  marine  turbines  are  much  the  same  as  the  others,  only  they  are  of  much  larger 
diameters  of  wheel,  and,  as  they  drive  usually  on  three  shafts,  one  or  more  of  them  has 
a  reversing  turbine  and  a  main  turbine  on  one  shaft  and  in  one  casing.  Probably  the 
application  of  the  steam  turbine  to  marine  propulsion  has  been  the  most  important 
step,  and  we  shall  therefore  fully  examine  the  various  inventions  of  Mr.  Parsons  for  this 
purpose.  The  applications  of  the  turbine  to  screw  propellers  and  their  arrangement 
in  the  ship  will  be  treated  in  the  chapter  on  "  Marine  Engineering." 

In  Patent  No.  14,476,  1899,  we  have  several  marine  steam  turbines  specified, 
principally  with  a  view  to  combining  ahead  with  astern  turbines.  As  no  turbine  has 
been  designed  to  drive  in  either  direction,  it  is  necessary  to  combine  two  turbines  to 
do  the  double  movement,  and  this  has  been  accomplished  by  Mr.  Parsons  in  several 
ways.  Thus  from  the  specification,  the  new  invention  comprises  a  combination  of 
main  steam  turbine  with  reversing  steam  turbine  in  which  the  main  turbine  and 
reversing  turbine  are  enclosed  within  a  casing  formed  in  one  piece,  or  within  a  casing 
formed  of  several  pieces  bolted  together,  the  exhaust  ends  of  both  main  and  reversing 
turbines  discharging  directly  into  the  condenser,  or  into  one  passage  leading  to  the 
condenser — a  combination  in  which  the  reversing  turbine  is  telescoped  within  the  main 
turbine  in  order  to  reduce  the  longitudinal  space  occupied,  and  the  reversing  turbine 
case  preferably  then  revolves  while  the  centre  part  is  fixed  ;  and  a  combination  in 
which  the  reversing  turbine  is  placed  at  the  steam  end  of  the  main  turbine,  and  the 
exhaust  from  the  reversing  turbine  passes  through  the  interior  of  the  main  turbine 
spindle  or  drum.  In  all  these  modifications  the  reversing  turbine  is  one  of  ordi- 
nary types,  and  it  is  run  in  the  vacuum  of  the  condenser  while  the  main  turbine  is 
in  operation. 

Referring  to  the  illustrations,  Fig.  179  is  a  sectional  elevation  of  a  main  and 
reversing  turbine  mounted  on  the  same  spindle,  and  arranged  and  constructed  according 
to  one  modification.  Turbines  end  to  end  are  used  in  this  case. 

Fig.  180  is  a  sectional  elevation  of  a  main  and  a  reversing  turbine  mounted  on  the 
same  spindle,  and  arranged  and  constructed  according  to  another  modification. 

Referring  in  the  first  place  to  Fig.  179,  a  is  the  main  turbine  enclosed  chiefly 
in  the  casing  c,  and  b  the  reversing  turbine  enclosed  in  the  inner  part  /  of  the 
casing  d,  the  casings  c  and  d  being  bolted  together  at  e.  The  main  turbine  a  is  of 
the  well-known  parallel  flow  type,  and  is  mounted  on  the  spindle  /",  which  also  carries 
the  reversing  turbine  b,  which  has  its  low  pressure  end  h  turned  towards  the  low 
pressure  end  g  of  the  main  turbine.  Both  low  pressure  ends  open  into  the  low  pressure 
casing  d,  and  discharge  by  the  same  passage  k  to  the  condenser ;  or  the  low  pressure 
casing  d  may  be  made  part  of  the  condenser  without  special  passages.  The  steam 
supply  for  the  main  turbine  enters  by  the  passage  n  ;  the  steam  supply  to  the  reversing 
turbine  is  carried  through  the  low  pressure  casing  d  by  a  separate  steam  pipe  m.  By 
this  arrangement  a  powerful  reversing  turbine  which  rotates  in  the  condenser  vacuum 


Marine  Steam  Turbines 


147 


when  the  main  engine  is  operating  the  spindle/" in  the  usual  direction,  e.g.>  for  propelling 
a  vessel  ahead,  is  provided. 

Instead  of  arranging  the  vacuum  ends  together,  the  reversing  motor  may  be  turned 
round,  placing  the  high  pressure  end  near  the  vacuum  end  of  the  main  engine,  while 
still  maintaining  the  separate  turbine  casing  /  within  the  low  pressure  casing  d  and 


FIG.  179. — Parsons'  Marine  Turbine. 

discharging  from  the  reversing  turbine  into  the  low  pressure  casing  as  before,  and  also 
running  the  reversing  turbine  in  the  condenser  vacuum  as  before  mentioned. 

Referring  now  to  Fig.  180,  which  illustrates  the  second  modification,  the  reversing 
turbine  b  is  here  telescoped  within  the  main  turbine  a  in  order  to  economise 
longitudinal  space.  The  spindle  f  carries  the  drums  o  and  7,  which  support  the 
rotating  blades  of  the  main  and  reversing  turbines  respectively.  The  fixed  blades  of 
the  main  turbine  are  attached  as  before  to  the  outside  casings  c  and  d>  and  those  of 


FIG.  180. — Parsons'  Telescoped  Marine  Turbine. 

the  reversing  turbine  are  fixed  on  the  outside  of  the  inner  cylinder  p,  which  is  preferably 
supported  from  the  exhaust  casing  d  by  projecting  arms  or  webs  q.  Steam  is  supplied 
to  the  reversing  turbine  by  a  pipe  or  pipes  r  inside,  or  forming  part  of  the  inner 
cylinder  p.  These  steam  pipes  may  serve  for  fixing  the  cylinder  p  to  the  end  of  the 
casing  d.  Instead  of  this  arrangement  the  steam  may  be  conveyed  to  the  reversing 
turbine  through  the  spindle  f  from  the  passage  n,  which  supplies  steam  to  the  main 
turbine  as  in  the  previous  modification. 


148 


Modern   Engines 


Another  form  of  turbine  is  shown  in  Fig.  181.  To  prevent  leakage  from  the  steam 
end  of  the  main  turbine  to  the  steam  end  of  the  reversing  turbine,  or  vice  versa,  at  points 
2  and  3  baffle  grooves  and  rings  are  formed  on  the  casing  c  alternating  with  a  series  of 
grooves  and  rings  on  the  ring  v  in  order  to  check  the  flow  of  steam,  and  holes  are 
provided  on  the  ring  v  to  allow  any  leak  of  steam  to  escape  into  the  condenser. 


FIG.  181. — Double-Ended  Marine  Turbine. 

In  all  the  modifications  the  reverse  turbine  runs  idly  in  the  vacuum  when  not  in  use. 

The  telescoping  arrangement  can,  of  course,  be  used  to  make  a  compact  turbine 
for  land  purposes. 

The  next  improvement,  made  in  conjunction  with  Mr.  Wass,  relates  to  connecting 
turbines  directly  to  condensers.  They  had  found  by  experiment  that  a  very  large 


FIG.  182. — Parsons'  Combined  Turbine  and  Condenser.     Section. 

proportion  of  the  total  energy  of  steam  can  be  obtained  with  a  steam  turbine  by 
expanding  to  a  very  low  pressure — such  a  pressure,  for  example,  as  one-thirtieth  of  an 
atmosphere.  By  this  a  turbine  is  found  to  give  considerably  increased  efficiency.  This 
increase  of  efficiency,  however,  is  easily  lost  by  introducing  a  slight  back  pressure,  and 
it  is  difficult  on  board  ship,  or  in  confined  spaces,  to  obtain  room  for  an  exhaust  pipe  of 
sufficiently  large  dimensions  to  prevent  injurious  throttling  of  the  exhaust. 


Marine  Steam  Turbines 


149 


The  invention  consists  in  entirely  dispensing-  with  connecting  pipes  between  the 
low  pressure  turbine  and  the  condenser,  and,  in  fact,  making  the  low  pressure  turbine 
and  the  condenser  in  one  part,  or  as  parts  of  the  structure  which  may  be  built  up  of 
several  parts,  the  condenser  being  formed  of  one  or  more  groups  of  tubes.  The  steam 
thus  leaves  the  low  pressure  turbine  blades  and  passes  directly  to  the  surface  condenser 
part  of  the  turbine  cylinder  without  any  intermediate  connecting  pipes  whatever. 

Referring-  now  to  the  illustrations — 

Fig-.  182  is  a  sectional  elevation  of  one  modification  of  the  invention,  in  which  a  low 
pressure  steam  turbine  is  bolted  to  a  surface  condenser. 

Fig-.  183  is  a  plan  of  the  same. 

a  is  the  turbine,  and  b  the  condenser.  The  casing  c  of  the  turbine  is  bolted  at  d 
to  the  end  e  of  the  condenser.  The  shaft /passes  through  the  turbine  and  condenser, 
and  is  supported  in  bearings  at  g  and  h.  kt  k  are  the  feet  or  supports  of  the  turbine 
and  condenser. 

The  steam  enters  the  turbine  at  /  and  passes  through  the  turbine  doing  work  and 
leaving-  the  last  vanes,  passes  at  m  into  the  condenser,  which  is  of  a  usual  construction. 
The  outlet  from  the  condenser  to  the  air  pump  is  shown  at  n.  The  circulating  water 


FIG.  183. — Plan  of  Turbine  and  Condenser. 

enters  the  condenser  at  ry  passing  into  the  end  space  p  ;  it  then  passes  up  through  the 
tubes  q  to  the  top  compartment  r,  whence  it  descends  through  the  tubes  .$•  to  the 
compartment  /,  and  leaves  the  condenser  at  u. 

The  low  pressure  blades  of  the  turbine  thus  revolve  at  but  a  short  distance  from  the 
surface  condensing  tubes,  and  no  resistance  is  experienced  in  passing  the  enormous 
volume  of  exhaust  steam  at  a  low  pressure  from  the  turbine  blades. 

By  this  arrangement  the  steam  expands  down  to  a  very  low  pressure  indeed, 
without  losing  the  effect  of  expansion  by  back  pressure  or  undue  resistance  between 
the  turbine  and  the  condenser. 

Mr.  Parsons  had  five  years  previously  patented  some  claims  for  this  utilisation 
of  very  low  pressures  in  his  turbine.  We  will  only  select  three  figures  from  the 
Specification,  No.  367,  1894.  This  invention  relates  to  a  combination  of  a  reciprocating 
steam  engine  with  a  steam  turbine,  and  its  object  is  to  increase  the  power  obtainable 
by  the  expansion  of  steam  beyond  the  limits  possible  in  reciprocating  engines.  He 
discovered  that  pressures  much  too  low  to  be  utilisable  in  the  low  pressure  cylinder  of 
a  reciprocating  condensing  engine  may  be  made  to  develop  very  considerable  power 
in  a  steam  turbine  of  simple  construction  specially  designed  for  low  pressures.  The 
invention  consists  in  combining  together  an  expansive  reciprocating  steam  engine 


Modern  Engines 


FIG.  184. — Parsons'  Combined  Engine  and  Turbine.     Plan. 


and  a  low  pressure  steam  turbine  in  such  a  manner  that  when  the  high  pressure  steam 
has  acted  in  the  reciprocating  engine,  and  has  been  expanded  as  much  as  possible  in 
the  low  pressure  cylinder,  it  passes  to  the  low  pressure  steam  turbine,  and  thence,  after 
further  expansion,  to  the  condenser. 

The  work  done  by  the  steam  in  the  cylinders  of  the  reciprocating  engine  is  thus 
supplemented  by  the  work  done  by  the  steam  turbine,  and  so  the  power  obtained 
from  a  given  weight  of  steam  is  largely  increased.  It  will  thus  be  seen  that  the 

turbine  forms  the  last  element  in 
the  series  of  apparatus  for  utilising 
the  energy  of  the  steam  on  its 
way  from  the  boiler  to  the  con- 
denser, thus  substantially  increas- 
ing the  efficiency  of  the  engine. 

Fig.  184  shows  in  plan  a  re- 
ciprocating compound  condensing 
marine  engine  E  combined  with 
the  low  pressure  turbine  B  ;  the 
turbine  being  utilised  for  any  power 
purposes  in  the  ship. 

The   turbine   B    may   drive    a 
dynamo  D  and  produce  electricity 
to   light   a   mill,    or    be    used    for 
working  centrifugal  pumps  or  fans 
for  forced  blast,  urging  the  fires,  or  any  other  purpose. 

A  section  of  the  turbine  B  is  shown  at  Fig.  185  coupled  directly  to  a  dynamo.  B  is 
the  low  pressure  turbine,  having  a  large  disc  B1  carrying  rings  of  blades  B3  on  both  sides 
of  it ;  these  rings  of  blades  alternate  with  rings  of  fixed  blades  in  the  turbine  case. 
The  exhaust  steam  from  the  condensing  engine  enters  the  turbine  by  the  passage  B2  as 
indicated  by  the  arrow  ;  it  passes  radially  outwards  through  the  rings  of  blades  on  both 
sides  of  the  disc  B1,  as  shown  by  the  arrows  i,  2,  3,  4.  The  disc  is  perforated  at  the  centre 
to  allow  the  steam  to 
pass  through.  From 
the  disc  the  steam 
passes  to  the  con- 
denser B4,  as  shown 
by  the  arrow  5.  D  _ 
is  a  dynamo  coupled 
directly  to  the  turbine 
spindle. 

Fig.  186  shows 
the  parallel  flow  tur- 
bine adapted  for  low 
pressures. 

In  Fig.  184  the  re- 
ciprocating compound 

condensing  engine  E  is  shown  in  plan  as  driving  the  propeller  shaft  H.  It  is 
supplied  with  high  pressure  steam  by  the  pipe  E1,  and  the  exhaust  steam  passes 
by  the  pipes  E2  to  the  condenser  G,  a  pipe  E3  from  the  exhaust  pipe  E2  supplies  low 
pressure  steam  to  the  low  pressure  turbine  B,  and  the  exhaust  from  the  turbine 
passes  by  way  of  the  pipe  E4  to  the  condenser  G.  In  this  case  the  turbine  B  is 
utilised  for  the  electric  lighting  of  the  ship,  and  it  actuates  the  dynamo  D  coupled 
directly  to  its  spindle. 

Instead  of,  or  in  conjunction  with,  the  dynamo,  the  turbine   may  drive  fans   for 


FIG.  185.— Section  of  Exhaust  Steam  Turbine.     Radial. 


Exhaust  Steam  Turbine 


ventilating  or  forced  draught  purposes,  or  pumps  for  circulating  water  or  discharging 
water  from  the  ship. 

Stop  valves  are  provided  to  enable  exhaust  steam  to  be  supplied  to  the  turbine,  so 


FIG.  1 86. —Section  of  Exhaust  Steam  Parallel  Turbine. 

that  the  whole  of  the  exhaust  steam  from  the  main  engines  may  be  passed  through  the 
turbine  if  required,  or  part  passed  to  the  turbine  and  part  to  the  condenser  direct. 

These  simple  forms  of  turbines  might,  and  no  doubt  will,  be  used  in  many  trades 
where  boiling  is  a  process  consuming  much  fuel,  the  waste  steam  from 
which  would  give  considerable  power  if  passed  through  a  turbine  into 
a  condenser. 

And  it  is  a  moot  question  whether  the  best  way  to  compound  an 
engine  with  high  pressure  reciprocating  pistons  would  be  to  connect 
it  with  a  turbine. 

In  any  case,  it  is  important  to  bear  in  mind  that  a  turbine,  work- 
ing with  steam  at  or  below  atmospheric  pressure  into  a  good  vacuum, 
recovers  a  great  deal  of  the  heat  energy. 

By  interposing  a  simple  turbine  in  the  exhaust  steam  pipe  between 
the  engine  and  condensers  in  compound  or  simple  reciprocating 
engines  it  may  pay  to  obtain  electric  light  in  that  way. 

BLADES   OR  VANES   OF   PARSONS'  TURBINES 

These  at  first  were  formed  by  milling  teeth  on  brass  discs, 
forming  flat  blades  with  a  passage  between  of  45°  angle  with  the 
shaft. 

These,  however,  were  not  highly  efficient,  as  the  steam  in  being 
deflected  was  partly  thrown  against  the  wrong  side  of  the  passages, 
thus  retarding  the  movement. 

By  properly  curving  the  blades  and  shaping  the  passages  the 
steam  in  passing  presses  wholly  on  one  side,  so  that  at  an  early  FIG.  187. 

date    Messrs.    Parsons    adopted   the   form   of  blades   shown   in   the 
illustrations. 

Fig.  187  is  a  view  of  the  blades  seen  end  on  as  arranged  on  a  turbine  wheel. 

The  invention  consists  in  forming  the  blades  upon  the  back,  that  is,  on  the  convex 
side  as  compared  with  the  concave  side,  with  a  thickening  or  projection  as  at  a  (Fig. 
187),  the  said  thickening  or  projection  being  nearer  to  the  edge  where  the  steam 
enters  than  where  it  discharges.  The  projection  a  tapers  off  to  both  edges,  but  more 


Modern  Engines 


FIG.  i 88. 


gradually  to  the  discharge  edge  than  the  admission  edge.     This  is  clearly  shown  at 
Fig.  187,  where  c  are  the  admission  edges  and  d  the  discharge  edges. 

By  this  modification  in  the  shape  of  these  curved  blades  a  passage  between  the 
blades  is  produced  in  which  the  minimum  of  loss  of  energy  occurs  presumably  by  the 
reduction  of  eddy  resistance,  but  possibly  in  other  ways.  In  any  case,  whatever  be 
the  correct  explanation,  an  improvement  of  about  at  least  10  per  cent,  was  found  in 
steam  consumption  by  altering  one  of  the  steam  turbines  in  this  manner. 

In  one  case,  for  ex- 
ample, a  moderate  amount 
of  thickening,  such  as  shown 
in  Fig.  187,  at  the  left-hand 
side,  gives  a  gain  of  12  per 
cent.  ;  and  that  a  greater 
'e  thickening,  such  as  shown 
at  the  right-hand  side,  gives 
a  better  result  still. 

These  blades  are  formed 
into  circles  or  segments  of 
circles  by  a  very  ingenious  and  simple  tool  patented  by  Mr.  Parsons  and  others. 

As  applied  to  the  parallel  flow  turbine,  suitable  strips  of  ductile  metal,  preferably 
brass,  are  bent  into  a  circle  or  sector  of  a  circle.  On  one  edge  of  the  strip 
teeth  of  a  special  shape  are  cut  by  mechanism.  The  form  of  the  teeth  is  such 
that  when  the  blade  sections  are  laid  in  the  grooves  and  the  teeth  turned  over  upon 
them  the  teeth  and  blades  fit  each  other  closely  and  form  a  secure  fastening  or 
mechanical  joint.  This  joint  is  sometimes  made  more  secure  by  notching  or  perforating 
the  blades  before  insertion,  so  as  to  interlock  with  the  strip.  One  or  more  rings  or 
shroudings  may  be  put  upon  the  blades.  The  blade  sector  so  formed  is  inserted  and 
caulked  into  grooves  in  the  turbine 
drums  and  cylinders,  or  is  other- 
wise secured  to  them. 

Referring  to  Figs.  188  to  190, 
a  is  a  heavy  shroud  having  teeth 
cut  into  one  side,  leaving,  however, 
sufficient  breadth  of  metal  uncut  to 
provide  a  strong  strip  to  serve  as 
base  for  the  blades  ;  b  is  a  light 
shroud  which  has  also  cut  teeth, 
but  the  uncut  breadth  is  less  than 
in  a.  c,  c,  c,  etc.,  are  blades  which 
are  laid  in  the  spaces  between  the 
teeth  of  the  two  shrouds,  and  each  tooth  is  closed  over  on  the  blade  held  by  it.  On  the 
right  of  Fig.  188  teeth  are  shown  in  the  position  occupied  before  closing  over  ;  the 
teeth  of  the  heavy  shroud  are  lettered  e,  e,  and  those  of  the  light  shroud  f,  f\  the  blades 
c,  c  are  notched  at  d  (Fig.  189),  and  the  light  shroud  engages  with  the  notches  as 
shown. 

The  bases  of  the  blades  may  be  also  notched  or  drilled  to  increase  the  grip  between 
the  teeth  of  the  heavy  shroud.  The  teeth  e,  e,f,f(Fig.  188)  are  formed  with  a  discon- 
tinuous outline  on  the  back,  so  that  when  bent  over  and  closed  on  the  top  of  the  blade 
the  convex  outline  shall  then  be  a  continuous  curve,  which  corresponds  exactly  with  the 
concave  surface  of  the  blade,  and  fits  that  surface.  By  this  means  the  teeth  bear  solidly 
all  over  the  ends  of  the  blades,  and  form  a  strong  continuous  sector  or  ring  as  shown. 

We  may  cut  the  notches  between  the  teeth  to  such  a  depth  that  the  teeth  when 
bent  over  will  project  above  the  blades,  and  the  surplus  metal  may  be  subsequently 


FIG.  i 


Turbine  Blades 


turned  off,  leaving  the  shroud  parallel,  so  as  to  exactly  fill  the  grooves  in  the  drums 
or  cylinders. 

Both   the   grooves   in   the   drums   and   cylinders,   and    also   the   shrouds,   may   be 
dovetailed  slightly  for  better  security,   and  when   the   blade   rings   have   been   placed 
in  position  the  teeth  e  are  separately 
expanded  by  caulking,  so  as  to  fill  the 
grooves  and  hold  the  blades  tightly. 
Sometimes  they  prefer  to  place  a  strip 
of   soft    metal    alongside    the    shroud 
in  the  groove,  and  caulk  the  strip  to 
secure  tightness  of  the  whole  structure. 

In  this  same  specification  plans 
for  casting  the  blades  into  shrouds 
are  described  and  illustrated,  but  the 
mechanical  method  is  seemingly  much 
preferable. 

In  Fig.  190,  given  in  Mr.  Par- 
sons' Glasgow  paper,  is  shown  the 


complete  construction  of  the  revolving 
wheels  in  the  three  sets  of  wheels  in 
one  casing,  the  top  half  of  which  has 
been  removed,  showing  the  curved 


FIG.  190. — Parsons'  Wheels. 


blades;  and  Fig.  191,  from  the  same  paper,  shows  one  of  the  sets  of  engines  for 
H.M.S.  Destroyer,  in  course  of  erection  ;  and  Fig.  192  the  complete  steam  turbine  now 
made  in  larsre  sizes. 


FlG.  191. — Parsons'  Marine  Turbines. 


DE   LAVAL  STEAM  TURBINES 

We  now  pass  on  to  the  other  pioneer  in  steam  turbines  who  struck  out  in  original 
lines  to  secure  efficiency.  In  the  early  'eighties  De  Laval  had  invented  cream  separators 
working  on  the  principle  of  centrifugal  force.  He  therefore,  in  order  to  get  the  highest 
practicable  value  for  this  force,  was  compelled  to  drive  the  separating  vessels  at 
enormous  speeds.  He  was  thus  brought  into  contact  with  the  difficulties  due  to  high 
speed  driving,  and  became  thus  practically  acquainted  with  them  ;  and,  as  a  direct  way  of 
obtaining  a  high  speed  from  steam  power,  he  used  a  Hero  turbine  directly  coupled  to  his 
cream  separator  shaft ;  and  from  these  beginnings  he  started  out  on  the  improvement 


154  Modern  Engines 


of  steam  turbines,  culminating  in  the  successful  production  of  a  wheel  and  nozzles 
constructed  and  operated  on  thoroughly  scientific  lines  and  with  novelty  therein. 

With  the  true  modesty  and  dignity  of  the  genuine  inventor,  the  first  important  patent 
is  contained  in  the  following  few  lines.  (Patent  7143,  1889)  : — 

"  My  invention  relates  to  an  improvement  in  turbines  which  are  set  in  motion  by 
means  of  a  current  of  steam  ;  and  the  object  of  the  improvement  is  to  increase, 
by  complete  expansion,  the  velocity  of  the  steam  current,  thus  producing  the  relatively 
largest  quantity  of  vis  viva  of  the  steam. 

I  attain  this  object  by  the  construction  of  the  steam  supply  pipe  in  such  a  manner 
that  the  cross  sections  of  the  same  are  slowly  increased  near  to  the  turbine  wheel  and 
in  the  direction  of  the  latter.  The  ratio  of  increasing  the  cross  sections  is  due  to  the 
proportion  and  distance  between  the  smallest  section  and  the  largest  one,  in  such  a 
manner  that  in  the  steam  passage  between  these  two  sections  a  permanent  current  of 
steam  is  produced  under  isoentropical  expansion. 

Referring  to  the  illustration,  Fig.  193,  a  front  view  and  side  elevation,  both  partly 
in  section,  which  shows  the  mouthpiece  of  a  steam  supply  M,  constructed  as  above 
described,  in  combination  with  a  turbine  wheel  A,  b  is  the  smallest  and  c  the  largest 
cross  section.  Between  both  these  sections  the  steam  expands  from  the  pressure  0.577  PO 
(P0  =  boiler  pressure)  to  the  pressure  of  the  receiver  (  =  P2). 


FIG.  192. — Parsons'  Steam  Turbine  (standard  large  sizes). 

Having  now  particularly  described  and  ascertained  the  nature  ot  my  said  invention, 
and  in  what  manner  it  is  to  be  performed,  I  declare  that  what  I  claim  is : — 

In  steam  turbines,  the  combination  of  the  turbine  wheel  with  a  steam  supply, 
the  cross  sections  of  which  increase  regularly  near  to  the  turbine  wheel  and  in  the 
direction  of  the  same,  substantially  as  and  for  the  purpose  specified." 

That's  all.  And  note  the  simple  explicit  drawings.  It  is  sate  to  say  that  if  this 
invention  had  originated  in  New  York,  the  specification  would  have  filled  some  pages 
of  this  book  and  the  claims  filled  more  space  than  De  Laval's  whole  specification,  while 
the  possibilities  offered  in  the  way  of  drawings  are  unlimited.  A  whole  series  of  pos- 
sible and  impossible  turbines  would  have  been  shown,  with  furnaces,  chimneys,  boilers, 
gas  works,  superheaters,  condensers,  and  every  conceivable  detail  carefully  drawn. 

De  Laval  accepted  the  high  speed  necessary  with  a  single  wheel,  and  formed  his 
nozzle  on  scientific  lines,  so  that  the  full  velocity  may  be  attained  as  already  described 
and  illustrated  under  "  Steam  Jets." 

Parsons  had  already  shown  that  elasticity  in  the  bearings  of  the  turbine  wheel 
shaft  was  necessary  to  damp  vibrations,  and  allow  the  wheels  to  approach  a  revolution 
round  the  centre  of  gravity ;  but  De  Laval  aimed  at  higher  peripheral  speeds,  and  so, 
instead  of  damping  vibration,  he  arranged  his  wheel  on  a  flexible  shaft  so  that  the  shaft 
could  bend  and  allow  the  wheel  to  find  its  own  centre  of  revolution.  This  flexible 


Single  Wheel  Steam  Turbines         155 

shaft  was  at  first  made  with  spring  actions,  but,  owing  to  the  fact  that  the  torque  of 
a  wheel  at  these  high  revolutions  is  small,  the  shaft  can  be  made  thin  enough  of  itself  to 
bend  sufficient  for  the  purposes.  The  first  specification  is  as  follows  : — 

The  invention  consists  of  an  improved  arrangement  for  reducing  to  a  minimum  the 
reactions  on  the  bearings  by  rapidly  rotating  bodies,  arising  from  their  imperfect  balancing. 
This  is  accomplished  by  fixing  the  rotating  body  either  directly  or  indirectly  on  a  tube  or 
sleeve  which  is  fixed  on  and  around  a  shaft,  which  tube  is  made  elastic  or  yielding  in  some 
suitable  manner,  so  that  the  rotating  body  is  rendered  self-adjusting  or  self-balancing. 
Two  constructions  of  this  arrangement  are  shown — 
Fig.  194  being  a  part  sectional  elevation  of  one  construction,  and 
Fig.  195  a  like  view  of  another  construction,  showing  a  transverse  sectional  view 
on  the  line  cd,  and  a  transverse  sectional  view  on  the  line  ab. 
Similar  letters  of  reference  indicate  corresponding  parts. 
In  Fig.  194  the  body  A  is  fixed  on  the  boss  B,  which  again  is  made  fast  upon  the 


Front  View.  Side  Elevation. 

FIG.  193. — De  Laval  Wheel  and  Nozzle. 

central  part  of  the  tube  or  sleeve  C,  the  latter  being  fastened  on  both  ends  D  and  E  to 
the  shaft  F.  This  shaft  is  shown  supported  at  each  end  in  bearings  G  and  H  in  the 
usual  way,  and  the  motion  is  imparted  to  the  system  by  means  of  the  driving  pulley  K. 
A  portion  of  the  shaft  F  between  D  and  E  has  been  turned  down,  thus  leaving  an 
annular  space  between  the  tube  C  and  the  shaft  F.  A  helical  slit  b  is  cut  in  the  tube  C 
between  its  central  portion  and  each  end,  so  that  the  central  portion  occupied  by  the 
body  A  may,  while  rotating,  assume  such  position  relative  to  shaft  F  as  may  be  required 
to  secure  an  even  rotation,  which  saves  wear  and  tear  in  the  bearings. 

In  Fig.  195,  where  the  body  A  is  directly  fixed  upon  the  thicker  central  portion  of 
the  tube  or  sleeve  C,  this  tube  is  made  elastic  or  yielding  as  required,  either  by  turning 
down  the  tube  until  its  thickness  is  considerably  reduced  (see  transverse  section  through 
ab},  or  the  tube,  being  somewhat  thicker  (see  transverse  section  through  cd),  is  provided 
with  longitudinal  slits  a  by  means  of  which  the  required  elasticity  is  obtained. 


156 


Modern  Engines 


The  bearings  for  the  ends  G  and  H  ot  the  shaft  have  in  the  present  cases  been 
shown  fixed.  In  some  instances,  however,  it  may  be  desirable  that  these  also  should 
be  able  to  yield  to  a  slight  extent.  In  such  cases  Seller's  bearings  should  be  used, 
pivoted  bearings,  or  bearings  surrounded  with  indiarubber  rings  like  the  top  bearing 
of  the  cream  separators.  Other  constructions  of  self-adjusting  bearings  may  also  be 
used  to  give  the  requisite  adjustment. 

In  a  subsequent  patent  De  Laval  shows  how  to  apply  this  flexible  shaft  with  special 
jointed  bearings  to  other  rapidly  moving  heavy  rotating  bodies,  so  that  a  balance  is 
obtained.  This  and  the  previous  patent  display  true  engineering  science,  in  which  a 
desirable  result  is  achieved  by  natural  means.  The  old-time  engineers,  when  they  first 
introduced  moderately  high  speed  engines,  tried  to  balance  the  cranks  by  counterweights 
and  other  means,  bringing  the  inertia  of  the  revolving  parts  into  opposition ;  but 
they  relied  upon  some  tons  of  cast  iron,  stone,  and  concrete,  and  ten  or  twelve  huge 
foundation  bolts,  after  all,  to  prevent  vibration.  They  did  not  cure  vibration  ;  they 
only  made  it  less  in  amplitude  by  mere  force,  and  the  internal  strains  were  greatly 
increased.  The  early  engines  were  kept  from  violent  vibration  by  brute  force,  not  by 
any  scientific  means.  Nowadays,  engineers  do  not  depend  on  foundations  for  smooth 
working :  a  good  engine  well  designed  and  balanced  should  run  full  speed  without  vibra- 


FIG.  194. — De  Laval  Flexible  Shaft. 


FlG.  195.— De  Laval  Flexible  Shaft. 


tion  when  standing  upon  a  foundation  without  any  holding  down  bolts.  A  high  speed 
engine  which  requires  to  be  held  down  to  a  huge  foundation  by  heavy  bolts  is  an  engine 
radically  wrong  in  design. 

A  theory  of  the  flexible  shaft  has  been  given  by  Mr.  Sandford  A.  Moss  in  Power, 
which  may  be  summed  up  as  follows  : — 

The  popular  explanation  of  the  phenomenon  is  that  the  flexible  shaft  allows  the 
disc  to  "rotate  about  its  centre  of  gravity."  This  is  not  true,  however,  since  in  all 
cases  a  disc  slightly  out  of  balance  rotates  so  that  the  shaft  is  slightly  deflected  and  the 
centre  of  gravity  is  away  from  the  centre  of  rotation.  The  outward  centrifugal  force  due 
to  this  eccentricity  of  the  centre  of  gravity  is  just  in  equilibrium  with  the  inward  pull 
due  to  the  deflection  of  the  shaft.  Of  course  this  deflection  causes  a  rotating  reaction 
at  the  bearings,  which  tends  to  vibrate  them,  and  which  usually  gives  trouble  in  high 
speed  machinery.  This  is  because  the  greater  the  speed  the  greater  the  centrifugal 
force,  and  ordinarily  the  greater  the  shaft  deflection  required  to  balance  it.  The 
increase  of  deflection  throws  the  centre  of  gravity  out  farther,  which  still  further  increases 
the  centrifugal  force.  Hence  ordinarily  the  reaction  on  the  bearings  due  to  the  shaft 
deflection,  which  is  of  course  equal  to  the  centrifugal  force,  increases  rapidly  with 
increase  of  speed.  However,  it  is  a  remarkable  fact  that,  after  a  certain  critical  speed 
has  been  reached,  the  shaft  deflection  and  the  reaction  on  the  bearings  actually  decrease 
as  the  speed  increases,  in  order  that  equilibrium  may  be  maintained  with  the  centrifugal 


De  Laval  Turbines  157 

force  due  to  the  corresponding1  eccentricity  of  the  centre  of  gravity.  The  eccentricity  is 
less  than  the  deflection,  instead  of  being  greater  as  ordinarily.  The  more  flexible  the 
shaft  the  less  this  "critical  period." 

By  using  a  very  flexible  shaft  and  running  it  at  a  much  greater  speed  than  the 
critical  speed,  the  deflection  required  to  maintain  equilibrium  with  the  centrifugal  force 
due  to  the  corresponding  eccentricity  of  the  centre  of  gravity  becomes  very  small  indeed, 
and  the  corresponding  rotating  reaction  pull  on  the  bearing  is  almost  imperceptible. 

The   critical   speed   in   radians   per  second   is   found   to   be   'A  =  \/lvf  >  wnerem  ^ 

is  the  natural  period  of  vibration  of  the  shaft  if  deflected  and  let  go  or  struck  in  the 
middle,  M  is  the  weight  of  the  disc  in  Ibs.,  and  K  the  force  required  to  deflect  it  unit 
distance. 

•  oo      /^2i6xr2v&  I  k 

In  revolutions  per  minute  this  becomes  — */  ^— - — — —  — ,  or  187.56*7  v^j  where  k  is 

.  2  7T    »  IVl  T      IVJ. 

load  in  Ibs.  required  to  deflect  the  shaft  i  inch  and  M  is  the  weight  of  the  disc  in  Ibs. 

Now  M/£  is  the  actual  deflection  of  the  shaft  in  inches,  produced  by  the  weights  of 

the  disc  ;   hence  the  critical   speed   is  -r- —  revolutions  per  minute,  where  d  is  the 

v« 

deflection  of  the  shaft  in  inches  produced  by  the  weight  of  the  disc. 

For  a  steel  shaft  of  the  same  diameter  throughout,  with  two  bearings  either  swivelled 
or  so  loose  that  the  shaft  may  be  considered  as  merely  supported  by  them,  and  for  a 
single  mass  fixed  at  any  point  between  the  bearings,  the  formula  reduces  to  the 
following:  Let  /  be  the  distance  between  bearings  in  inches,  M  the  weight  in  Ibs.  of 
the  rotating  mass,  a  its  distance  from  either  of  the  bearings  in  inches,  and  d  the  shaft 
diameter  in  inches  ;  then  the  critical  speed  at  which  the  maximum  vibration  occurs,  in 

d2         I~T 
revolutions  per  minute,  is  387,700-— r*/  — .     This  also  gives  the  period  of  a  natural 

G\L  —  d ]    *      JV1 

vibration.  If  there  are  two  rotary  masses,  there  are  two  distinct  vibration  periods  and 
critical  speeds.  Now  as  to  the  efficiency  of  such  wheels,  as  mentioned  previously, 
it  is  important  that  as  much  as  possible  of  the  kinetic  energy  of  the  steam  jet 
issuing"  from  the  nozzle  should  be  taken  up  by  the  turbine  wheel,  and  thus  trans- 
formed into  mechanical  energy.  The  angle  between  the  nozzle  and  the  plane  of 
rotation  of  the  wheel  is  20  degrees,  and  in  order  to  obtain  the  maximum  efficiency 
the  peripheral  speed  of  the  turbine  wheel,  i.e.  the  linear  velocity  of  the  buckets, 
should  be  34  per  cent,  of  the  velocity  of  the  steam.  •  The  absolute  velocity  of 
the  steam  leaving  the  buckets  is  then  34  per  cent,  of  the  initial  velocity,  and  the 
energy  absorbed  by  the  turbine  wheel  is  88  per  cent,  of  the  kinetic  energy  of  the 
steam. 

If,  for  instance,  the  speed  of  the  steam  entering  the  buckets  of  the  turbine  wheel  is 
4000  feet  per  second,  the  speed  of  the  steam  leaving1  the  buckets  should  be  1360  feet 

per  second,  and  the  number  of  horse-power  per  Ib.  of  steam  —± 2— — =  u  ;  and  the 

*g  x  55°  x  3600 

steam  consumption  per  theoretical  horse-power  — £ — ^5 3 =  9.1  Ibs. 

40oo2-  1360* 

The  steam  nozzles  are  placed  in  very  close  proximity  to  the  buckets  of  the  turbine 
wheel,  in  fact  the  distance  is  only  2  millimetres,  or  about  TY  of  an  inch,  and  consequently 
there  is  practically  no  loss  of  velocity  between  the  steam  jet  leaving  the  nozzle  and 
entering  the  buckets  of  the  turbine  wheel,  nor  leakage  of  steam. 

The  speed  of  the  turbine  wheel,  which  for  a  velocity  of  the  steam  jet  of  4000  feet 
per  second  ought  to  be  about  1880  feet  per  second,  or  about  21  miles  per  minute,  is, 
however,  much  lower,  for  several  practical  reasons.  At  the  present  time  the  peripheral 
speed  of  the  De  Laval  turbine  wheel  does  not  exceed  1380  feet  per  second,  which  should 


Modern  Engines 


make  a  steam  consumption  of  9.8  Ibs.  per  theoretical  horse-power.     The  following  table 
gives  the  speed  of  some  types  of  turbine  wheels  : — 

TABLE   XVI.— SPEEDS   OF  THE   TURBINE   WHEELS. 


Size  of  Engine. 

Middle  Diameter  of  Wheel. 

Revolutions  per 
Minute. 

Peripheral  Speed. 
Feet  per  Second. 

Horse-power. 

Millimetres.             Inches. 

5 

100                          4 

30,000 

515 

15 

150                          f, 

24,000 

617 

3° 

225                          8| 

20,000 

774 

So 

300                         ii  J 

16,400 

846 

100 

500                         19! 

13,000 

i"5 

300 

760                        30 

10,600 

1378 

Fig.  196  shows  the  stresses  in  a  wheel  for  a  50  horse-power  steam  turbine. 
As  may  be  seen  by  this  diagram,  the  wheel  is  so  constructed  that  both  P  the  radial 
stress  and  S  the  tangential  stress  have  their  largest  value  at  the  circumference  of  the 
wheel,  just  where  the  buckets  are  fixed.     Consequently  the  wheel  is  not  made  of  uniform 
strength,  but  is  strongest  at  the  heavy  part,  that  is,  in  the  centre. 

It  will  be  seen  from  Fig.  196  that  the  tangential  stresses  S  in  the  boss  of  the  wheel 
increase  as  they  approach  the  hole  in  the  centre  of  the  wheel.  These  stresses  would  be 
still  greater  on  the  larger  sizes  of  wheels,  and  in  order  to  avoid  these  greater  stresses  the 
larger  wheels  are  made  without  any  hole  through  the  centre,  but  the  shaft  is  made  in 
two  pieces  fixed  to  the  wheel  by  flanges  and  screws.  Fig.  197  shows  the  arrangement 

of  small  and  medium 
turbine  wheels  ;  and 
the  arrangement  of  the 
larger  turbine  wheels 
is  shown  in  Fig.  198. 
The  part  of  the 
turbine  which  makes 
it  possible  to  run  the 


^ 


FIG.  196. — Curves  of  Stresses. 


turbine  wheel  at  its 
enormous  speed  is  the 
"flexible shaft."  The 
shaft  on  which  the 
turbine  wheel  is 
mounted  has  bearings 
on  each  side  of  the 


wheel  at  a  good  distance  from  it,  and  the  shaft  is  consequently  flexible  and  can  allow  the 
wheel  to  swing  a  little  in  its  plane  of  rotation.  No  matter  with  what  nicety  the  turbine 
wheel  may  be  turned  and  balanced,  it  is  practically  impossible  to  bring  the  centre  of 
gravity  of  the  wheel  exactly  into  the  geometrical  centre  round  which  the  wheel  revolves. 

The  flexible  shaft  and  the  turbine  wheel  are  so  proportioned  that  the  settling  of  the 
wheel  takes  place  very  quickly,  and  the  critical  speed  is  from  \  to  £  of  the  standard 
number  of  revolutions  of  the  wheel.  Of  course  the  turbine  wheels  are  very  finely 
balanced,  and  the  settling  of  the  wheel  is  therefore  scarcely  perceptible.  It  is  the  flexible 
shaft  that  serves  to  transmit  the  power  of  the  turbine. 

The  diameter  of  the  shaft  is,  on  account  of  the  high  speed,  very  small,  and  it  is 
therefore  easy  to  make  it  flexible.  The  shaft  of  the  300  horse-power  turbine  wheel  has 
a  diameter  of  34  millimetres,  or  iT5F  inch,  and  that  of  the  150  horse-power  wheel  25 
millimetres,  or  i  inch  :  no  larger  diameter  is  required. 


De  Laval  Turbines 


IS9 


The  normal  speed  of  the  turbine  wheel  is  too  high  for  direct  driving  of  ordinary 
machinery,  and  it  is  therefore  reduced  by  means  of  gearing.  This  gearing  is  made  on 
the  double  helical  system,  and  machined  with  the  greatest  care  and  accuracy,  as  is 
necessary  on  account  of  the  high  speed.  The  speed  of  the  gearing,  that  is  the  linear 
velocity  of  the  teeth,  is  about  1000  feet  per  second.  The  pinion  is  made  of  hard  steel 
(in  one  piece  with  the  shaft),  and  the  teeth  of  the  gear- 
ing wheels  are  cut  in  a  somewhat  softer  steel  than  the 
pinion. 

All  the  revolving  parts  of  the  turbine  are  most  care- 
fully balanced,  and  the  parts  mounted  on  the  shafts  are 
centred  by  tapers. 
Thebearingsofthe 
slow  speed  shafts 
are  lubricated  by 
rings,  as  is  usual 
in  this  class  of 
machinery.  The 
journals  of  the 
flexible  shaft  are 
oiled  by  sight  feed 
lubricators.  The 
bearings,  which 
are  all  made  as 


FlG.  197. — Arrangement  of  Small  and 
Medium  Turbine  Wheels. 


FIG.  198.  — Arrangement  of  Large 
Turbine  Wheels. 


interchangeable 

bushes,   are  lined 

with  white  metal, 

and  there  is  practically  no  wear  on  them  if  the  machine  is  well  lined  up  and  properly 

mounted  from  the  beginning. 

The  turbines  are  generally  fitted  with  more  than  one  steam  nozzle,  and  these  are 
arranged  at  intervals  in  a  ring  in  close  proximity  to  the  turbine  wheel,  receiving  the 
steam  from  a  steam  chest  in  the  turbine  case.  Each  nozzle  is  usually  provided  with  a 


USD 


FIG.  199. — Valve  and  Nozzle  of  De  Laval  Turbine. 

shutting-off  valve,  so  that  any  nozzle  can  be  closed  or  opened  at  any  time.  This 
arrangement  is  of  considerable  advantage,  as  when  the  turbine  is  working  at  reduced 
load  some  of  the  nozzles  may  be  closed  and  a  high  efficiency  of  the  machine  maintained, 
even  although  it  is  not  working  at  full  load.  This  will  be  more  plainly  understood  from 
the  tests  of  steam  consumption,  which  will  be  noticed  subsequently.  The  arrangement  of 
a  nozzle  and  its  valve  will  be  seen  from  Figs.  199  and  200. 


i6o 


Modern   Enines 


As  may  be  seen  from  the  foregoing  table,  the  peripheral  speed  increases  with  the  size 
of  the  wheel,  and  the  larger  the  diameter  the  higher  also  is  the  peripheral  speed.  The 
300  horse-power  turbine  wheel  runs  with  a  peripheral  speed  of  1378  feet  per  second  in  the 
middle  of  the  buckets  ;  the  outside  diameter  of  this  wheel  is  800  millimetres,  or  31^  inches, 
and  the  circumferential  velocity  of  the  wheel  is  1450  feet  per  second,  or  more  than  16 
miles  per  minute.  At  this  speed  the  wheel  would  travel  round  the  equator  of  the  earth 
in  25  hours. 

On  account  of  the  peripheral  speed  of  the  turbine  wheel  not  being  so  high  as  it 
theoretically  ought  to  be,  there  is,  particularly  at  high  admission  pressure  and  good 
vacuum,  a  slight  impact  when  the  steam  enters  the  buckets.  This  is,  however,  allowed, 
for  practical  reasons,  and  the  energy  due  to  the  loss  of  speed  by  this  impact  is  not 
entirely  lost  by  the  turbine,  as  will  be  seen  later. 

One  advantage  of  the  action  principle  of  the  turbine  is  that  the  turbine  wheel  can 

revolve  quite  freely  in 
the  casing.  This  is 
an  essential  feature 
of  the  machine,  and, 
moreover,  it  would 
not  be  possible  to  run 
at  the  speed  required 
should  a  tightening  be 
necessary  round  the 
turbine  wheel.  The 
wheel  does  not  touch 
anywhere,  and  all  the 
steam  on  emerging 
from  the  nozzles  must 
.  pass  the  buckets  of  the 
wheel,  as  the  radial 
length  of  the  buckets  is 
always  larger  than  the 
diameter  of  the  steam 
jet.  There  is  conse- 
quently no  possibility 
of  any  steam  leaking 
through  the  turbine, 
but  it  must  of  neces- 
sity pass  the  buckets 
and  deliver  its  energy 
to  the  turbine  wheel. 

The  high  peripheral  speed  which,  as  previously  seen,  is  necessary  in  order  to  obtain 
a  good  efficiency  has  been  obtained  by  allowing  the  turbine  wheel  to  run  at  a  very  high 
velocity.  A  reference  to  Table  XVI.  will  also  show  that  the  number  of  revolutions  is 
much  higher  than  the  speeds  formerly  used  in  practical  engineering. 

The  wheel  is  made  as  a  solid  disc,  on  the  circumference  of  which  the  buckets 
are  dovetailed  in,  each  bucket  being  made  and  fixed  separately  to  the  wheel.  The 
buckets  consequently  load  the  circumference  of  the  wheel  with  a  radial  force  when 
the  wheel  is  revolving.  The  amount  of  this  force  may  be  understood  when  it  is 
mentioned  that  the  centrifugal  force  on  the  bucket  of  a  300  horse-power  turbine  wheel, 
which  bucket  weighs  250  grains,  is  15  cwts.  when  the  wheel  is  running  at  its  standard 
speed. 

The  stresses  in  the  wheel  are  tangential  and  radial ;  and  if  we  call  the  radial  stress  P 
and  the  tangential  stresses  S,  it  is  evident  that  both  P  and  S  vary  with  the  radius  R. 


FIG.  200. — De  Laval  Wheel  and  Nozzles. 


De  Laval  Turbines 


161 


Further,  these  stresses  depend  on  the  axial  thickness  of  the  wheel  in  each  place,  and 
they  also  affect  one  another. 

Before  the  admission  steam  can  enter  the  steam  chest  and  pass  from  thence  to  the 
nozzles  it  is  regulated  by  the  governor  valve,  which  in  its  turn  is  controlled  by  the 
centrifugal  governor  of  the  machine.  The  governor  valve  is  a  balanced  double-seated 
valve,  connected  with  a  link  motion  to  the  centrifugal  governor. 


Longitudinal  Section. 


Sectional  Plan. 
FlG.  201. — De  Laval  Turbine. 

The  general  arrangement  of  the  machine  will  be  understood  from  Fig.  201,  which 
shows  a  turbine  in  section  and  plan,  and  Fig.  202,  a  dissected  turbine. 

The  speed  of  the  turbine  is  regulated   by  a   very  sensitive   centrifugal  governor, 

mounted   horizontally  on  the  end  of  the  gear-wheel  shaft.     The  moving  parts  of  the 

governor  work  practically  without  friction,  and  it  is  therefore  very  quick  and  powerful. 

This  governor  is 'very  simple,  although  the   construction    may  seem   peculiar,  and  its 

VOL.  i. — ii 


162 


Modern   Engines 


dimensions  are  very  small  on  account  of  the  comparatively  high  speed  at  which  it  works. 
Fig.  203  gives  an  idea  of  the  construction  of  the  governor. 

The  variation  of  speed  between  full  load  and  no  load  is  nearly  i  per  cent. ;  the 
variation  is  from  2  to  3  per  cent,  generally. 

The  standard  sizes  of  steam  turbines  can  work  with  any  steam  pressure  between  50 
and  200  Ibs.  per  square  inch,  and  either  with  or  without  vacuum.  The  only  parts  of  the 
machine  which  have  to  be  arranged  to  suit  the  admission  pressure  and  the  pressure  in 


A  Turbine  shaft 

B  Turbine  wheel 

C  Pinion 

D  End  bush 

E  Safety  bearing  in  turbine  box 

F  Middle  bush  in  two  parts 

G  Safety  bearing  in  box  covers 

H  Ball  bush  with  adjusting  spring 

I    Steam  nozzle 

K  Stuffing  box  with  stop  valve  to  nozzle 

L  Wheel  to  valve  spindle 


M  Gear  wheel 
N  Gear  wheel  shaft 

O  Gear  wheel  shaft  bushes  in  two  parts 
P  Lubricating  ring 
Q  Centrifugal  governor 
R  Driving  pulley 

S   Stop   nut   with    pulley   for  connect- 
ing to  tachometer 
T  Tightening  bush  in  two  parts 
U  Adjusting  nut  with  spring 
V  Friction  gland 


FIG.  202. — Loose  Parts  of  Steam  Turbine. 

the  exhaust  are  the  steam  nozzles,  which  have  to  be  shaped  according  to  the  amount  of 
expansion  of  the  steam.  The  nozzles  are  made  interchangeable — all  other  parts  do  not 
alter  with  the  pressure, — and  the  machine  can  consequently  work  with  any  pressure 
between  the  above  limits,  if  only  the  turbine  case  is  provided  with  suitable  nozzles.  The 
turbine  can  also  be  arranged  with  nozzles  for  running  both  condensing  and  non- 
condensing  :  this  is  very  handy  and  convenient,  particularly  if  the  turbine  drives  its  own 
condensing  machinery,  direct  or  electrically. 

As  the  question  of  economy  became  of  more  importance,  the  size  of  the  wheels  and 

also  the  number  of  revo- 
lutions in  the  larger  unit 
of  machine  are  so  pro- 
portioned that,  with  in- 
creasing unit,  the  velocity 
of  the  vanes  of  the  wheel 
approached  more  closely 


FIG.  203. — Governor  of  De  Laval  Turbine. 


to  what  it  theoretically 
ought  to  be.  The 
and  the  sections  of  the 


stresses  are  largest  in  the  circumference  of  the  wheel, 
wheel  were  so  proportioned  that  the  stresses  increased  with  the  radius.  This  was 
done  in  order  that  the  wheel  might  be  weakest  in  the  circumference  where  the  vanes 
were  fixed,  and  in  order  to  be  still  more  certain  on  this  point  a  recess  was  turned  in 
this  outer  portion  of  the  wheel.  Should  a  wheel  burst  on  account  of  too  high  a  speed  it 
gave  out  at  the  recess,  the  vanes  became  detached,  and  the  steam  could  not  longer  drive 


De  Laval  Turbines 


163 


the  wheel.  The  buckets  of  the  detached  parts  of  the  wheel  were  so  light  that  they 
could  do  no  damage,  and  the  machine  only  stopped  running.  With  this  type  of  wheel  the 
heavy  central  part  had  never  burst.  Indeed  it  would  be  a  very  serious  matter  if  the  heavy 
part  ever  became  detached  from  the  shaft.  When  the  calculations  for  a  new  wheel  were 
completed,  the  material  of  which  the  wheel  had  to  be  made  was  tested  in  order  to  see 
whether  its  strength  corresponded  to  that  on  which  the  calculations  were  based.  If 
agreement  existed,  the  wheel  was  then  made,  and  run  until  it  burst  at  the  periphery. 
Experience  had  proved  that  the  speed  at  which  the  breaking  of  the  wheel  took  place 
could  be  calculated  beforehand,  and,  if  the  speed  obtained  by  experiment  accorded  with 
the  theoretical  result,  the  wheel  was  adopted  as  a  standard  for  that  particular  type  for 
practical  use.  The  wheels  were  generally  proportioned  so  that  breaking  would  take 
place  when  the  wheel  was  running  at  about  double  the  number  of  revolutions  required  in 
actual  work  ;  consequently  it  could  hardly  happen  in  practice  that  the  machine  increased 
so  much  in  speed  that  there  would  be  any  danger  from  the  wheel  breaking  at  its 
circumference.  In  order  to  keep  the  stresses  down  in  the  central  parts,  the  wheels  were 
made  very  thick  towards  the  axis.  If  a  wheel  of  the  same  thickness  throughout  were 
used,  the  stresses  would  be  very  great  at  the  centre,  and  this  was  a  matter  to  avoid  in 
high  speed  machinery.  It  was  best  to  do  away  as  much  as  possible  with  the  drilling 


tifj 


FIG.  204. — Skin  Friction  Curve. 


of  holes  for  bolts,  etc.  in  the  boss  of  a  wheel,  as  holes  considerably  weakened  the  central 
parts,  and  it  was  very  often  the  boss  which  had  to  keep  the  wheel  together.  As  to  the 
resistance  to  which  the  revolving  wheel  was  subjected  from  the  surrounding  medium, 
this  depends  partly  on  the  skin  friction,  and  partly  also  to  eddy  making.  It  was  found 
in  practice  that  the  resistance  was  almost  exactly  proportional  to  the  density  of  the 
surrounding  medium,  and  that  it  increased  approximately  with  the  fifth  power  of  the 
diameter  and  the  third  power  of  the  number  of  revolutions.  It  was  therefore  evident 
that  the  thinner  the  medium  which  surrounded  the  wheel,  the  less  would  be  the  resistance 
offered  to  its  motion,  and  this  would  be  plainly  understood  from  the  curves  in  Fig.  204. 
The  resistance  was  less  in  saturated  steam  than  in  air  of  the  same  pressure,  and  it 
decreased  with  increasing  vacuum.  A  150  horse-power  turbine  wheel  was  subjected  to  a 
resistance  of  35  horse-power  when  running  in  steam  of  i  atmosphere  absolute  pressure, 
but  if  it  were  run  in  a  vacuum  of  28  inches  of  mercury — 2  inches  of  mercury  absolute 
pressure — the  resistance  would  be  decreased  in  about  the  same  proportion,  and  would 
be  5^  *35  =  2j  horse-power,  a  gain  of  32^  horse-power.  The  velocity  of  the  steam  jet 
into  the  vacuum  was,  moreover,  higher  than  the  velocity  of  outflow  into  the  atmosphere, 
and  both  these  circumstances  made  it  essential  that  the  turbine  machinery  should  be  run 
under  vacuum.  From  Fig.  204  it  was  also  evident  that  the  resistance  was  less  in  super- 
heated than  in  saturated  steam,  and  that  it  decreased  with  the  amount  of  superheating. 


1 64  Modern   Engines 


The  frontispiece  of  this  volume  illustrates  two  fans  driven  by  two  of  these  turbines 
installed  at  Romford  Gas  Works. 

Plate  VI.  illustrates  the  smaller  sizes  set  up  with  reducing  belt  gearing  all  self- 
contained  for  driving  small  powers  :  this  illustrates  a  5  horse-power  set. 

And  Plate  VII.  illustrates  the  large  Parsons'  turbine  with  alternator  attached. 
The  frontispiece  and  Plate  VI.  are  from  Messrs.  Greenwood  &  Batley,  who  are  the 
British  representatives  and  manufacturers  of  De  Laval  turbines. 

Before  passing  on  to  notice  the  few  turbines  introduced  since  the  great  success  of 
Parsons  and  De  Laval,  it  may  be  of  interest  to  notice  another  effect  of  high  velocities  in 
rotating  bodies,  namely  the  gyrostatic  effects :  the  inertia  of  a  body  opposing  any  force 
which  tends  to  set  it  in  motion,  or  to  alter  its  motion  while  moving,  either  in  direction  or 
velocity. 

The  gyroscope  illustrates  these  properties  beautifully.  The  gyroscope  usually 
consists  of  a  fly-wheel  mounted  on  centres  inside  of  a  ring,  so  that  it  can  be  spun  round 
at  a  high  velocity.  It  is  sold  as  an  interesting  toy,  but  some  of  the  most  intricate 
mechanical  problems  can  be  found  in  its  theory.  It  is  also  of  use  for  showing  the 
earth's  rotation. 

A  bicycle  wheel  may  be  used  to  demonstrate  a  few  effects  of  the  gyroscope.  The 
rear  wheel  is  usually  easily  removed  with  its  spindle.  If  this  is  done  and  two  people 
hold  it  up,  one  grasping  each  end  of  the  spindle,  and  the  wheel  be  rapidly  spun  round, 
it  will  be  found  to  strongly  resist  any  attempt  to  twist  the  shaft  round,  out  of  the  line  it 
was  held  in.  One  of  the  persons  may  let  go  his  end  of  the  spindle,  the  wheel  will  not 
fall,  and  the  other  person  will  not  have  to  exert  any  more  support  than  that  required  to 
keep  the  weight  of  one  end  up.  In  fact,  the  wheel,  while  rotating  in  a  vertical  plane, 
can  be  suspended  by  a  string  tied  to  one  end  of  the  spindle.  The  spindle  will  not  drop 
out  of  the  horizontal  position,  even  although  supported  at  one  end  only. 

If  a  gyroscope  be  taken  between  the  two  hands,  or  the  spinning  bicycle  wheel 
between  two  persons,  and  the  wheel  turned  right  over,  so  that  the  spindle  is  turned  end 
for  end,  a  considerable  resistance  will  be  offered  by  the  wheel  to  this  operation.  The 
mathematical  explanation  for  this  resistance  is  complicated,  but  the  simplest  way  to  look 
at  it  practically  is  to  consider  the  direction  of  the  motion  of  the  wheel,  first  before  it  is 
turned  over,  and  after.  Suppose  a  person  looking  on  one  side  of  the  wheel  when  it  first 
spins  round,  that  he  sees  the  direction  of  rotation  is  from  left  to  right,  that  is  clockwise, 
he  will  find,  on  turning  the  spindle  end  for  end  against  the  resistance  of  the  wheel,  that 
the  motion  or  direction  of  rotation  has  from  his  point  of  view  reversed.  The  resistance 
offered  by  the  wheel  is  the  resistance  which  a  body  in  motion  offers  to  reversal  of  the 
direction  of  the  motion,  just  as  a  jet  of  steam  or  water  resists  reversal  in  the  bucket  of  a 
turbine. 

In  fast  running  machinery  like  steam  turbines,  any  alteration  of  the  plane  of  revolu- 
tion is  accompanied  by  resistance  which  bears  on  the  shaft  and  bearings.  In  ships  the 
shaft  is  horizontal,  so  that  any  quick  turning  of  the  ship  will  throw  pressure  on  the 
turbine  bearings  resisting  the  turning  round  of  the  ship.  Rolling  of  the  ship  would  not 
have  any  effect,  for  the  plane  of  rotation  would  not  be  altered  by  a  ship's  rolling  with 
the  turbine  shaft  fore  and  aft.  Pitching  would  have  but  a  slight  effect,  for  the  angle  of 
movement  is  small.  A  rapid  deviation  of  the  ship  at  full  speed  from  her  course  would 
have  most  effect ;  and  in  ships  of  high  speed  and  light  weight,  such  as  torpedo-boats  and 
destroyers,  with  powerful  engines  and  powerful  steering  gear,  it  is  quite  possible  that  a 
sudden  swerve  would  throw  a  dangerous  amount  of  strain  on  the  turbine  bearings,  and 
might  bring  about  a  rupture  of  the  structure. 

A  rolling  ship  with  the  turbine  shaft  athwart  the  ship  would  also  be  subjected  to 
straining,  for  the  rolling  would  considerably  and  quickly  alter  the  plane  of  rotation. 

Experiments  with  gyroscopes  are  now  mostly  made  with  electrically  propelled  wheels,, 
the  motion  being  steady,  and  prolonged  as  long  as  we  please. 


Rateau  Turbine 


There  are  three  or  four  turbines  which  have  been  introduced  into  practice,  while 
there  are  some  three  or  four  thousand  which  have  not  been  reduced  to  practice.  Since 
Parsons  and  De  Laval  established  the  practicability  of  steam  turbines  fitted  with  proper 
bearings,  guide  blades,  and  wheel  shafts  and  other  things,  all  designed  with  strict  regard 
to  the  elastic  fluid  and  high  velocities  necessary,  there  has  been  the  usual  avalanche  of 
patents  poured  into  the  patent  offices.  About  fifty  patents  were  granted  in  1901,  and 
now  in  1903  only  four  or  five  of  them  have  ever  since  been  heard  of. 

I  have  tried  to  go  through  all  the  patents  since  1890  up  to  the  latest  published. 
Ninety-nine  out  of  every  hundred  are  utterly  sterile  of  any  original  ideas.  Many  are  not 
so  far  advanced  as  Pilbrow  and  Wilson  were  fifty  years  ago.  The  fact  is,  when  we  add 
Parsons'  improvements  and  De  Laval's  improvements  to  those  of  Pilbrow  and  Wilson, 
we  have  the  whole  state  of  the  art  and  science  of  steam  turbine  construction  at  the 
present  moment  clearly  founded  on  the  published  specifications  of  these  four  inventors. 

The  master  patents  having  expired  by  lapse  of  time,  the  vast  number  of  new  patents 
can  only  cover  some 
detail,  such  as  bearings, 
valves,  packing,  special 
nozzles  or  blades,  so 
that  all  recent  turbines 
are  either  Parsons'or  De 
Laval's,  with  some  sub- 
ordinate feature  altered 
or  changed  for  another. 

Some  of  them,  if 
equally  skilfully  de- 
signed and  equally  well 
made,  would  no  doubt 
give  as  good  results, 
but  that  "if"  is  of  a 
large  order. 

The  Rateau  turbine 
is  essentially  a  number 
of  De  Laval  turbines  in 
series  with  one  common 
shaft,  and  is  one  of  the 
first  rank,  designed  by 
Professor  Rateau.  Its 

scientific  points  are  above  criticism  ;  and,  made  with  that  mechanical  skill  which  French 
mechanics  display  in  all  their  work,  it  has  rapidly  assumed  an  important  position.  In 
Engineering  a  brief  description  of  it  as  given  by  Professor  Rateau  himself  is  as  follows: — 

The  multicellular  turbine  in  question  is  constructed  by  Messrs.  Sautter-Harl6  & 
Co.,  engineers,  of  Paris,  and  consists,  as  shown  in  Fig.  205,  of  a  series  of  rotating  wheels 
keyed  on  the  turbine  shaft,  and  separated  by  circumferential  diaphragms  held  in  grooves 
inside  the  turbine  casing.  The  latter  is  in  two  parts,  the  section  being  on  a  plane  which 
passes  through  the  axis  of  the  turbine.  This  allows  the  accurate  fitting  of  the  lower  halt 
of  the  system,  which  is  then  completed  by  putting  in  place  the  top  half  of  the  casing. 

The  wheels  consist  of  buckled  steel  plates,  conical  in  shape  (Fig.  205),  on  the  periphery 
of  which  are  riveted  nickel-steel  blades,  which  are  further  held  in  place  by  a  band.  The 
fixed  blades  of  the  distributors  (guide  blades)  are  fitted  on  the  periphery  of  the  diaphragms 
(see  2,  Fig.  205),  opposite  the  wheels.  On  Fig.  205  the  last  diaphragm  is  hatched  in 
order  to  throw  it  up  more  clearly. 

The  shaft  runs  through  the  diaphragms  in  bushes  of  anti-friction  metal,  with  but 
little  play — originally  two-tenths  of  i  millimetre.  The  shaft,  however,  makes  its  play 


FIG.  205. — Rateau  Turbine. 


i66 


Modern   Engines 


when  this  is  insufficient.  There  is  no  inconvenience  attached  to  the  friction  of  the  shaft 
in  the  anti-friction  bushes.  Leakages  of  steam  outside  the  distributors  can  only  take 
place  through  this  small  windage,  the  total  section  of  which  is  comparatively  a  very 
small  one,  owing  to  the  small  diameter  of  the  shaft.  The  space  between  the  wheels  and 
the  fixed  parts  is  from  3  to  6  millimetres  .118  inch  to  .236  inch;  there  is  thus  no 
fear  of  their  coming  into  contact.  Should  this  happen,  however,  and  a  number  of  blades 
get  broken,  they  could  easily  be  repaired,  even  on  board  ship,  as  each  blade  can  be 
removed  individually  and  be  replaced  by  another,  fixed  by  one  rivet  only. 

The  steam  flows  through  the  diaphragms  and  wheels  from  the  inlet  at  AB  to  the 
exhaust  G,  its  pressure  decreasing  progressively,  each  successive  wheel  working  under  a 
low  fall  in  pressure.  The  number  of  wheels  varies  from  three  to  four  only  to  thirty  and 
over. 

The  foregoing  shows  that  all  loss  in  efficiency  through  leakage  between  the  fixed 
and  movable  parts  has  been  prevented  in  a  marked  degree.  It  has  been  stated  that  with 
this  system  of  turbine  the  friction  of  the  wheels  in  steam  leads  to  a  notable  loss.  This  is 


188  Z£J  #02 

ElecinvaJ/  HJP:  measured/  out/ 
Th&Curwes correspond/  Co  the?  use*  of  steam? 

FIG.  206. — Results  of  Tests  on  Rateau  Turbine. 

not  the  case  ;  and  in  actual  practice,  with  a  turbine  the  dimensions  of  which  have  been 
carefully  calculated,  the  loss  by  steam  friction  is  only  3  to  4  per  cent,  of  the  power  of  the 
machine. 

The  steam  consumption  is  also  very  moderate,  being,  it  is  believed,  lower  than 
that  of  any  other  similar  type  of  engine.  These  turbines  are  calculated  with  great 
precision,  by  formulae  based  on  theory  and  completed  by  experiments  on  the  flow  of 
steam  ;  the  difference  between  the  calculated  figures  and  the  results  obtained  at  the 
trials  does  not  generally  exceed  2  per  cent. ,  thus  confirming  the  formulae  on  which  the 
etudes  were  first  made. 

The  efficiency  of  the  turbines  is  shown  in  the  diagram,  Fig.  206,  which  gives  the 
results  obtained  at  trial  runs  made  with  the  first  of  three  turbines,  coupled  to  a  continuous 
current  dynamo,  supplied  by  Messrs.  Sautter-Hade"  &  Co.  for  the  generating  station  of 
a  mine  at  Penarroya,  in  Spain.  The  only  motive  engines  in  this  station  are  the  three 
steam  turbines  in  question. 

From  the  diagram,  Fig.  206,  it  will  be  seen  that  the  consumption  of  the  turbine 
and  dynamo  under  full  load  or  500  horse-power — the  inlet  pressure  being  8.5  kilogrammes 


Rateau  Turbine  167 

per  square  centimetre  or  120  Ibs.  per  square  inch,  and  the  back  pressure  at  the  condenser 
.115  kilogramme  per  square  centimetre  (1.63  Ib.  absolute) — was  7.03  kilogrammes  or 
15.5  Ibs.  of  steam  per  electric  horse-power  hour  ;  and  under  an  overload,  at  640  horse- 
power, with  1 1  kilogrammes  or  156.5  Ibs.  per  square  inch  and  .128  kilogramme  or  1.82  Ib. 
absolute  counter  pressure  at  the  condenser,  the  steam  consumption  was  only  6.74  kilo- 
grammes or  15  Ibs.  of  steam  per  electric  horse-power  hour.  These  are  good  results  for  a 
500  horse-power  engine,  seeing  especially  that  the  vacuum  at  the  condenser  was  not 
very  high.  With  a  high  vacuum,  such  as  the  Hon.  Charles  A.  Parsons  can  so  readily 
obtain,  say  0.06  kilogramme  or  0.86  Ib.  absolute  back  pressure  at  the  condenser,  the 
above  figures  of  steam  consumption  would  be  reduced  by  10  per  cent,  at  least,  and 
would  be  14  Ibs.  per  electric  horse-power  hour  normally,  and  13.4  Ibs.  with  an  overload. 

The  diagram,  Fig.  206,  shows  further  that  the  total  efficiency  of  the  set,  which 
rises  to  58  per  cent,  at  full  load,  remains  approximately  constant  down  to  below  half 
load  ;  further,  the  total  consumption  of  steam — the  dynamo  remaining  excited  and  being 
self-exciting — does  not  exceed  336  kilogrammes  (740  Ibs.)  per  hour  running  empty,  being 
thus  10  per  cent,  lower  than  at  full  load.  M.  Rateau  believes  that  no  other  engine  gives 
such  favourable  results. 

It  is  an  impulse  turbine,  but  the  distinction  between  impulse  turbines  when  put  in 
series  order  and  so-called  reaction  turbines,  as  Mr.  Parsons  has  very  properly  pointed 
out,  is  the  difference  between  tweedledee  and  tweedledum,  when  the  fluid  is  steam. 
M.  Rateau  denies  this,  and  refers  to  hydraulics  to  show  the  difference.  But  water  and 
steam  are  two  very  different  fluids.  While  they  act  similarly  in  some  respects,  they 
differ  very  materially  in  others,  due  to  the  fact  that  one  is  elastic  and  the  other  is  not. 

OTHER  STEAM  TURBINES 

There  is  the  Stumpf  turbine,  a  modification  of  the  De  Laval,  with  a  wheel  more  like 
a  Pelton  wheel,  and  nozzles  all  around. 

The  Seger  turbine  is  like  Pilbrow's  2-wheel  machine  shown  in  Fig.  161,  and  my 
own  wheels  shown  in  Fig.  163.  A  feature  of  this  machine  is  the  reduction  of  the  speed 
by  belt  gearing. 

There  is  also  the  Schulz  and  Curtis  steam  turbines  ;  but  a  perusal  of  the  specifications 
reveals  nothing  of  much  novelty  in  either,  but  we  shall  have  occasion  to  examine  them. 

The  Westinghouse  Company's  steam  turbine  is  a  modification  of  Parsons'.  At  an 
early  date  this  company  purchased  the  American  rights  and  licence  for  the  British. 
The  Thomson-Houston  Company  in  this  country  supply  the  Curtis  turbine  as  modified 
by  the  engineers  of  the  General  Electric  Company  of  America  at  Schenectady. 

German  turbines  are  known  as  those  of  Professor  Stumpf,  and  Schulz.  French 
turbines  as  designed  by  Rateau  are  made  by  Sautter-Harte  &  Co.;  while  De  Laval 
turbines  are  made  in  many  countries. 

These  turbines  we  notice  here  more  for  the  purpose  of  showing  the  small  details 
which  distinguish  them  from  the  earlier  and  more  original  turbines. 

The  construction  of  high  speed  wheels  with  curved  blades  has  always  been  some- 
what a  difficulty.  We  have  seen  how  Parsons  and  De  Laval  make  their  wheels. 
E.  Seger,  of  Stockholm,  in  his  patent  of  1894,  No.  4611,  shows  a  simple  method  for 
forming  wheels  for  high  velocities  ;  he  employs  two  wheels  side  by  side,  like  Pilbrow's, 
Fig.  161,  running  in  opposite  directions. 

The  following  are  the  instructions  for  manufacturing  the  wheels,  in  which  the  vanes 
or  buckets  are  called  paddles  : — 

Referring  to  the  illustrations — 

Fig.  207  is  a  vertical  section  of  two  turbine  wheels  arranged  one  above  the  other; 

Fig.  207A  is  a  front  elevation  of  the  same  with  the  wheel  ring  partly  removed. 

Fig.  208  illustrates  the  form  of  the  paddle  blanks. 


i68 


Modern  Engines 


Fig.  2o8A  is  a  sectional  view  of  part  of  a  turbine  wheel  with  an  inserted  paddle,  but 
without  the  outer  wheel  ring. 

Fig.  209  is  a  side  elevation  of  a  part  of  such  a  turbine  wheel  with  paddles,  illustrat- 
ing two  different  steps  of  the  operation  of  fastening  the  latter. 

Fig.  2OQA  shows  a  part  of  such  a  turbine  wheel  with  the  paddles  fixed  by  riveting,  and 

Fig.  2096  shows  the  outside  of  a  part  of  the  wheel  body  with  notches  for  the  paddles, 
some  of  the  paddles  being  inserted. 

The  paddle  blanks  a,  which  may  be  punched  out  of  thin  sheet-iron  plates  or  of 


p£/&P 


7 

L 

7 

1 

</ 


FIG.  207. 


FIG.  207A. 


a 


FIG.  208. 


FIG.  209. 


plates  of  some  similar  material,  have  preferably  a  substantially  rectangular  form  (Fig.  208), 
with  a  notch  b  in  its  undermost  side.  The  lower  corners  of  this  rectangle  may  be  cut 
off  (as  is  illustrated  by  Fig.  208),  or  they  may  be  formed  in  some  other  way  in  such  a 
manner  that  they  do  not  overlap  the  edge  of  the  wheel  body  when  the  undermost  part  of 
the  paddle  blank  is  bent,  as  will  be  hereinafter  further  described.  The  body  of  the  wheel 

has  an  I-shaped  section  (Fig.  207),  and  at  the  two 

edges   of  the   wheel  ring  c   there  is   a   number   of 

notches   d  (Fig.   2oyA),  of  which  those  at  the  one 

edge   converge   towards   those   of  the   other   edge, 

without,  however,  meeting  the  same.     Into  the  said 

notches  the  flaps  x  on  both  sides  of  the  notch  b  are 

inserted,   the  paddle  blank  being  previously  some- 

what  curved.     If  the   turbine  is  a   compound  tur- 

bine,   consisting   of    two    turbine   wheels,    the   one 

above   the   other   (as   illustrated   in    Figs.   207   and 

207A),  the  notches  d  of  the  upper  wheel  must  have 

a    sharper    convergence    than    those   of  the   lower 

wheel.     After  the  insertion  of  the  paddle  blanks  in 

the  notches  the  ends  of  the  flaps  x  projecting  be- 

yond the  inside  of  the  wheel  ring  are  bent  against 

the  inside  of  that  ring  (Fig.  209),  thus  causing  the 

paddles   to    be   securely   held   in    position   even   at 

the   greatest   velocity  of  the   wheel.       In   order   to 

strengthen  still  further  this  fastening,  rings  e  may 

be   placed   inside  the  bent  paddle  ends  (Fig.  207), 

and  a  ring/  may  also  be  shrunk  on  around  the  outer 

ends   of  the   fixed   paddles    (Fig.    207),   care   being 

taken  to  give  the  paddle  ends  such  a  form,  either 

convex  or  concave,  that  the  wheel  ring  during  the 

shrinking  on  obtains  a  corresponding  form  and  is 

thus  more  securely  held  in  position. 
Instead  of  bending  over  the  inner  ends  of  the  paddle  blanks  (Fig.  209),  they  may  be 
fastened  to  the  wheel  body  by  riveting  their  ends  as  illustrated  in  Fig.  2O9A. 

His  next  improvement  consists  of  a  method  for  coupling  the  two  wheels  to  one  shaft 
by  a  speed  reducing  gear.  He  prefers  belt  gearing  for  the  purpose,  and  the  method  is 
thus  shown  and  described. 

The  inventor  is  aware  of  the  fact  that  a  single  belt  curved  round  pulleys  has  been 
used  in  this  way  before.  He  claims  as  new  the  fact  that  he  delivers  the  power  to  the 


FlG.  2CX)A. 


FIG.  2o8A. 


FIG.  2098. 


Seger's  Turbine 


169 


belt  by  two  pulleys,  one  on  each  turbine  wheel  shaft  to  a  fast  pulley  on  the  shaft  to  be 
driven,  and  a  loose  pulley  which  acts  as  guide  pulley,  and  is  made  movable  in  order  to 
tighten  the  belt  when  necessary. 

There  can  be  no  doubt  that  for  small  powers  a  belt,  if  well  chosen  of  right  material 
and  proper  breadth  and  thickness,  can  be  expected  to  give  good  results  in  the  double 
duty  of  reducing  speed  and  transmitting  the  power  of  two  wheels  to  one  shaft. 

In  steam  turbines  the  power  is  usually  transmitted  from  the  turbine  shaft  to  the 
main  shaft  by  means  of  toothed  gearing  ;  the  gear  teeth,  owing  to  their  great  velocity, 
frequently  break,  rendering  the  motor  unserviceable.  For  this  reason  the  use  of  a 
belt  for  the  power  transmission  is  preferable,  more  especially  as  a  broken  belt  can  be 
replaced  or  repaired  without  appreciable  expense  or  loss  of  time. 


End  View. 


Longitudinal  Section. 


FIG.  210.  —  Seger  Turbine. 


Referring  to  the  illustrations — 

Fig.  210  illustrates  a  longitudinal  section  of  a  compound  steam  turbine  provided 
with  the  arrangement  referred  to,  and  an  end  view  (partially  in  section)  of  the  same. 

a  and  b  are  the  two  turbine  wheels  which  by  the  steam  passing  through  are  caused 
to  revolve  in  opposite  directions,  as  indicated  by  the  arrows  in  the  Figures.  Their 
shafts  c  and  d  (which  are  horizontal  in  the  turbine  illustrated)  point  in  opposite  direc- 
tions, and  on  each  of  them  is  secured  a  belt  pulley  £,  f,  of  a  diameter  proportioned  to 
the  respective  velocities  of  the  two  turbine  wheels  so  as  to  give  the  same  velocity  to  the 
peripheries  of  the  two  pulleys.  Below,  above,  or  at  one  side  of  these  wheels  there  are 
placed  two  pulleys  £•  A,  one  of  these  (h  in  the  drawing)  being  fixed  to  a  shaft  i  rotating  in 
fixed  bearings  and  provided  with  a  driving  pulley  k.  The  other  pulley  g,  on  the  other 
hand,  is  secured  to  a  short  shaft,  which  may  also  be  journalled  in  a  fixed  bearing,  though 


IJO 


Modern   Engines 


the  better  plan  is  to  journal  it,  as  shown  in  the  drawing,  in  a  sliding  carriage  /  arranged 
in  the  engine  frame  in  such  a  manner  that  it  can  be  moved  towards  or  from  the  axis  of 
the  turbine  wheels,  thus  retaining  an  even  tension  in  the  belt  wrapped  around  the  pulley 
ir.  When  the  latter  is  located  below  the  turbine  wheels  so  as  to  be  suspended  in  the 
belt,  as  in  the  drawing,  it  will  maintain  an  even  tension  on  the  belt  by  virtue  of  its  own 
weight ;  if  this  is  not  the  case,  the  tension  may  be  kept  uniform  by  means  of  a  spring  or 
weight  tending  to  force  the  carriage  together  with  the  pulley  g  outward  from  the  axis  of 
the  turbine  wheels.  Around  the  4  pulleys  £,  f,  gy  and  h  is  wrapped  a  belt  passing  from 
the  pulley/around  the  reverse  side  of  the  pulley  g;  then  over  the  pulley  e  on  the  same 
side  as  over/",  and  finally  reaching  the  pulley/" on  passing  around  the  reverse  side  of  the 
pulley  h.  By  this  method  the  power  is  transmitted  from  the  turbine  wheels,  rotating  in 
opposite  directions,  to  the  shaft  i  and  the  driving  pulley  attached  to  it. 

We  may  next  notice  the  patents  of  Mr.  Richard  Schulz,  of  1900,  No.  21,472.     His 

ambition  is  to  replace  marine  engines  by  turbines 
and  balance  the  axial  thrusts.  He  starts  out  in 
November  1900  to  tell  us  what  Parsons  had  long 
ago  demonstrated  on  land  and  sea.  He  says  : — 


FIG.  211. — Schulz  Radial  Turbine,  with 
Reversing-  Turbine. 


FiG.  212.— Schulz  Radial  Turbine. 


"Steam  turbines,  on  account  of  the  regular  force  which  they  exert  upon  a  shaft, 
possess  many  advantages  over  steam  engines  with  reciprocating  pistons. 

There  are,  however,  considerable  drawbacks  in  the  ordinary  construction  of  steam 
turbines  in  comparison  with  steam  engines,  on  account  of  the  very  considerable  axial 
pressure  which  is  imparted  to  the  shaft  under  certain  circumstances. 

In  order  to  avoid  this  axial  pressure,  two  similar  steam  turbines  have  been  mounted 
on  the  same  shaft  symmetrically  side  by  side,  to  exert  an  axial  pressure  in  opposite 
directions.  Such  double  steam  turbines,  however,  require  much  room  and  are  of  great 
weight,  and  cannot  work  so  economically  as  only  a  single  turbine.  Counter  pressure 
discs  firmly  connected  with  the  shaft  have  been  employed  in  the  case  of  steam  turbines, 
with  turbine  coils  arranged  axially  one  behind  the  other,  and  also  in  steam  turbines  with 
radially  arranged  turbine  coils  in  which  the  counter  pressure  discs  are  encountered  by 
the  steam  in  an  opposite  direction  to  the  turbine  body,  thus  preventing  an  axial  pressure 
which  tends  to  displace  the  turbine  body  in  the  casing. 


Schulz  Turbines 


171 


In  addition  to  the  fact  that  the  arrangement  of  such  discs  is  a  drawback 
because  they  take  up  space,  there  is  also  the  impossibility  of  rendering-  these  discs 
steam-tight  on  the  periphery,  and  consequently  a  considerable  loss  of  steam  is  un- 
avoidable. 

These  drawbacks  are  avoided  by  the  arrangement  of  steam  turbines  which  form 
the  object  of  the  present  invention,  and  which,  in  the  first  place,  are  intended  for 
replacing  marine  engines.  The  arrangement  is  characterised  by  a  smaller  turbine 
working  under  a  higher  steam  pressure,  and  a  larger  turbine  working  under  lower 
steam  pressure  being  arranged  on  one  or  more  shafts  in  such  a  way  that  their  axial 
pressures  take  place  in  opposite  directions,  in  order  to  entirely  remove  the  resultant 
effective  axial  pressure  falling  on  the  bearings,  or  to  prevent  it  at  least  to  a  sufficient 
extent." 

In  one  form  of  construction  of  steam  turbines  (Fig.  213)  turbine  coils  are  axially 
arranged,  having  a  smaller  diameter  in  the  turbine  body  which  works  at  a  higher 
pressure,  and  a  greater  diameter  in  the  turbine  body  which  works  at  a  lower  pressure. 
The  two  turbine  bodies  a  and 
b  are  mounted  on  the  same 
shaft  c,  preferably  in  a  rigid 
casing  d. 

The  steam  enters 
through  a  nozzle  e  arranged 
about  the  centre  of  the  length 
of  the  casing,  and  impinges 
against  the  vanes  of  the 
smaller  turbine  a,  and  quits 
this  latter  through  an  over- 


flow passage/,  passing  into  the 

inlet  passage  h  of  the  larger 

turbine   b   through    a   pipe   k 

provided    with    a    regulating 

valve  g.     This  larger  turbine  is  traversed  with  steam  of  lower  pressure  in  a  direction 

opposite  to  that  in  which  it   flows   through   the   smaller   turbine ;    the   steam   finally 


FIG.  213. — Schulz  Axial  Turbine,  with  Reversing  Turbine. 


quitting  the  compound  turbine  through  a  discharge  pipe  z. 

The  direction  of  the  vanes  in  both  turbines,  and  the  direction  of  the  guide 
passages  in  the  casing,  must  of  course  be  so  selected  as  to  correspond  with  the  desired 
direction  of  rotation  of  the  shaft. 

The  regulating  valve  g  in  the  overflow  passage  may,  in  case  of  need,  retain  a 
portion  of  the  steam  escaping  from  the  smaller  turbine,  and  produce  a  higher  steam 
pressure  behind  the  said  turbine  and  diminish  the  pressure  of  the  steam  flowing  towards 
the  larger  turbine  through  the  free  opening  of  the  valve.  By  adjusting  this  regulating 
valve,  the  resultant  axial  pressure  on  the  shaft  which  falls  on  the  bearings  may  be 
altered  within  certain  limits.  By  means  of  guide  vanes  or  coils  /  provided  on  one  end 
wall  of  the  casing,  which  is  also  formed  into  an  exit  passage,  an  additional  turbine 
is  formed  for  backing,  which  is  necessary  to  enable  ships  to  be  manoeuvred.  In 
this  case  fresh  steam  flows  through  an  inlet  pipe  m  on  to  the  smallest  of  these  con- 
centric turbine  coils,  and  passes  out  of  the  largest  turbine  coil  into  the  exit  passage  in 
the  casing  end.  When  the  movement  is  in  a  forward  direction,  this  backing  turbine 
runs  without  deleterious  action  in  the  diminished  pressure  of  the  exhaust  or  discharge 
steam. 

In  another  somewhat  similar  form  of  construction  of  steam  turbine  provided  with 
high  pressure  and  low  pressure  turbine  coils,  such  as  shown  in  Fig.  214,  these  coils 
increase  in  size  in  the  direction  of  the  flow  of  the  steam.  A  similar  arrangement  may 
also  be  adopted  if  the  turbine  coils  arranged  one  behind  the  other  become  smaller  in 


172 


Modern   Engines 


diameter  instead  of  increasing-  in  diameter  in  the  direction  of  the  flow  of  steam,  or  if  a 
portion  of  the  turbine  coils  have  approximately  a  constant  diameter,  whilst  the  rest 
increase  or  decrease  in  diameter  as  required.  Schulz's  radial  flow  turbine  is  shown  in 
Fig.  211,  in  which  the  high  pressure  turbine  a  and  the  low  pressure  turbine  b  are  provided 
with  discs  of  different  sizes  fixed  on  the  shaft  c  of  the  engine  in  the  casing  d,  which  discs 
carry  radially  arranged  turbine  vanes.  These  two  discs  carry  on  the  sides  facing1  one 
another  a  larger  number  of  turbine  vanes,  for  the  guidance  of  which  guide  passages  or 
coils  are  provided  on  the  opposite  walls  of  the  casing  d.  In  this  case  also  the  steam 
enters  through  a  pipe  e  lying  approximately  at  the  middle  of  the  casing,  and  quits  the 
high  pressure  turbine  a  through  an  overflow  pipe  f  provided  with  a  regulating  valve  g, 
and  passes  through  an  inlet  passage  h  into  the  low  pressure  turbine  b,  and  finally  quits 
the  combined  turbine  through  an  exit  passage  i  at  the  outside.  In  the  example  shown 
the  steam  passes  into  the  high  pressure  turbine  a  and  also  into  the  low  pressure  turbine 
b  at  the  smaller  of  the  concentric  turbine  coils,  and  passes  out  at  the  largest  of  the 
turbine  coils.  The  disc  of  the  low  pressure  turbine  b  carries  on  its  reverse  side,  near  its 
periphery,  suitable  vanes  for  a  backing  or  reversing  turbine  /.  The  fresh  steam  enters 
through  an  inlet  pipe  m  here  also  at  the  smallest  of  the  concentric  turbine  coils,  and 
escapes  into  the  exit  passage  i  from  the  largest  of  the  turbine  coils. 

In  another  arrangement  shown  in  Fig.  212  both  the  high  and  low  pressure  turbines  a 
and  b  are  provided  with  several  discs  fixed  on  the  driving"  shaft  c  in  the  casing  d,  which 
discs  carry  turbine  vanes  on  both  sides.  The  steam  passes  through  the  inlet  pipe  e 

lying  approximately  at  the 
middle  of  the  length  of  the 
casing,  first  into  the  smallest 
disc  of  the  high  pressure  tur- 
bine a,  and  quits  the  latter 
at  the  larger  disc  in  order 
to  pass  through  an  overflow 
passage  f  provided  with  a 
regulating  valve  or  device  gy 
and  through  a  pipe  k  into  the 
inlet  passage  h  to  the  low 
pressure  turbine  b,  finally 
quitting  the  latter  at  the 
largest  disc  through  an  exit 
passage  i. 

If    it    be    necessary    to 

arrange  this  form  as  a  backing  or  reversing  turbine,  this  may  be  easily  done  in  the  same 
way  as  in  the  examples  previously  described. 

Of  course  the  compound  turbine  may  be  composed  of  more  than  two  turbine 
bodies.  According  to  the  foregoing,  the  arrangement  may  easily  be  such  that  the 
resulting  axial  pressure  which  is  imparted  to  the  shaft  c  and  the  bearing  n  may  be 
brought  to  the  desired  minimum.  The  same  result  is  also  easily  attained  by  the 
foregoing  if  the  separate  turbine  bodies  work  in  separate  casings,  and  if  they  are 
also  distributed  over  several  shafts.  Arrangements  for  regulating  turbines  are  given 
as  follows : — 

The  lever  which  works  the  rod  17  (Fig.  215)  may  also  be  connected  with  a  powerful 
governor  in  case  the  adjustment  of  the  annular  slides  is  to  take  place  automatically. 
Further,  in  the  normal  position  of  the  revoluble  slide  8  (Fig.  216),  in  which  position  all 
the  openings  are  exposed,  as  well  as  in  any  other  position,  the  section  of  passage  of 
each  separate  guide  blade  ring  7  may  also  be  suitably  diminished  or  increased  by  turning 
the  latter  itself,  as  the  edges  of  the  respective  guide  vane  openings  pass  more  or  less 
beneath  the  imperforate  portions  of  the  respective  slide  8.  The  pressure  of  the  steam 


FIG.  214. — Schulz  Axial  Turbine,  with  Reversing  Turbine. 


Schulz  Turbines 


173 


17 


on  entering  a  fresh  turbine  compartment  may  thus  be  reduced  from  the  first  to  a  given 
extent. 

In  the  case  of  a  steam  supply  which  only  extends  to  a  portion  of  the  circuit  in  which 
the  guide  vanes  and  the  steam  passages  formed  by  them  are  distributed,  for  instance,  by 
a  distribution  of  the  inlet  apertures  in  the  guide  blade  ring  7  in  the  manner  shown  in 
Fig.  215,  the  annular  slide  8  has  the  form  shown  in  Fig.  215.  In  a  normal  position 
(greatest  effectiveness)  the  openings  of  the  annular  slide  8 
lie  over  the  openings  in  the  guide  blade  ring  7  which 
forms  its  seat,  but  when  displaced  relatively  to  the  guide 
blade  ring  7  the  openings  of  the  latter  are  successively 
covered  by  the  imperforate  portions  of  the  slide. 

In  the  radial  turbine  shown  in  Fig.  216  the  arrange- 
ment of  the  annular  slide  8  and  its 
seat  is  such  that  an  exactly  similar 
action   of  steam  distribution  is  ob- 
tained. 

15  here  indicates  the  guide 
vanes  which  are  fixed  on  the  walls 
of  the  casing,  and  2  the  pres- 
sure vanes  of  the  turbine  bodies 
mounted  on  a  shaft  passing  through 
the  various  compartments  of  the 
casing.  The  relative  adjustment  FIG.  215.— Revoluble  Slide  of  Schulz  Turbine, 

of    the    annular    slides    8    is    here 

effected  by  means  of  shaft  17,  which  is  passed  upwards  through  the  walls  of  the 
turbine  casing  and  carries  toothed  segments  20,  which  engage  with  teeth  on  the  annular 
slides  8  (Fig.  215). 

The   steam   enters   through  a  pipe  socket   at   one  end  of  the  casing  against  the 

turbine  body  of  smallest  diameter,  and  escapes 
from  the  casing  through  a  pipe  socket  in  the 
cover. 

In  the  regulating  device  hereinbefore  described, 
in  which,  in  addition  to 
/^      i4*H  the     regulation    of    the 

steam  consumption  to 
correspond  with  the  ef- 
fectiveness of  the  work, 
a  second  regulation  is 
possible  by  the  adjust- 
ment of  the  guide  blade 
ring  7  of  the  annular 
slide  8,  a  subsequent 
improvement  of  the  cal- 
culated and  effective 
steam  sections  is  pos- 
sible also  for  the  greatest 

resultant  power,  which  is  very  valuable  for  compound  steam  turbines.  By  this  means 
it  is  possible  to  diminish  or  enlarge  the  inflow  apertures  for  each  separate  turbine 
body  separately  until  the  correct  pressure  forming  the  basis  of  the  calculation  on  the 
entrance  of  the  steam  into  the  turbine  bodies  is  actually  attained,  which  may  be 
ascertained  by  means  of  a  manometer. 

The  arguments  set  forth  for  the  necessity  for  the  improvements  above  described  the 
patentee  sets  forth  as  follow : — 


FlG.  216. — Schulz  Turbine  Blades  and  Guide  Blades. 


74 


Modern  Engines 


"  Steam  turbines  having"  several  rings  of  blades,  whether  axially  or  radially 
arranged,  work  with  comparatively  great  economy  only  so  long  as  they  develop 
their  greatest  effectiveness  when  the  sections  of  the  steam  passages  are  calculated 
for  this  greatest  effectiveness,  so  that  the  steam  enters  the  first  ring  of  the  turbine 
at  as  high  a  pressure  as  possible,  and  only  gradually  loses  pressure  in  its  passage 
through  the  others.  If,  however,  temporarily  a  less  amount  of  power  is  required 
from  the  same  turbine  with  the  same  size  or  section  of  the  steam  passages,  and  a 
suitably  diminished  quantity  of  steam  is  conveyed  to  the  turbine  by  the  action  of 
a  throttle  valve,  the  steam  on  its  entrance  into  the  first  ring  of  the  turbine 
has  already  lost  too  much  pressure,  and  therefore  is  utilised  uneconomically.  In 
order  to  avoid  this  drawback,  by  the  present  invention  the  sections  of  the  steam 
passages  are  regulated  to  correspond  with  the  desired  effectiveness  or  work  re- 
quired. For  this  object,  in  front  of  all  the  rings  of  guide  blades  or  vanes,  or  in  front 
of  some  of  them,  annular  slides  with  openings  or  apertures  are  arranged  in  such  a 
way  that  with  a  given  position  of  the  annular  slide  a  larger  or  smaller  number  of 
openings  to  the  steam  passages  which  are  formed  by  the  guide  vanes  and  pressure 
vanes  may  be  closed. 

In  a  turbine  which  replaces  marine  engines  it  is  more  particularly  advantageous 


FIG.  217. — Schulz  Turbine  Complete. 

to  adopt  a  diameter  for  the  turbine  bodies  forming1  the  combined  turbine,  by  which  still 
an  effective  pressure  in  the  direction  of  the  shaft  results  during  the  travel  of  the  turbine 
in  order  to  strain  the  bearings  n  of  the  shaft  as  little  as  possible.  This  effective 
pressure  is  directed  backwards  when  the  turbine  is  so  used,  and  must  be  so  selected 
that  it  approximately  equals  the  impulse  given  to  the  propeller  in  a  forward  direction. 
It  is  advisable  to  attach  manometers  at  suitable  places  on  the  high  and  low  pressure 
turbines  a  and  b,  in  order  to  permit  of  the  steam  pressure  being  ascertained  at  any 
time.  By  means  of  the  valves  or  regulating  devices  g  arranged  in  the  overflow 
passage  f  between  the  high  and  low  pressure  turbines,  small  alterations  in  the 
pressure  of  the  steam  behind  the  high  pressure  turbine  body  a  and  in  front  of  the 
low  pressure  turbine  body  b  may  be  easily  effected  by  observing  the  steam  pressures 
in  the  manometer." 

He  then,  in  1901,  proceeds  to  show  how  to  regulate  the  power  of  turbines,  by 
regulating  the  sections  of  the  steam  jet,  by  a  method  about  fifty  years  old,  as  applied 
to  water  turbines  of  impulse  type,  i.e.  by  sliding  disc  or  ring  covering  more  or  less  of 
the  steam  ports  or  passages. 

In  the  construction  shown  in  Figs.  218  and  219  a  shaft  i  carries  five  turbine  bodies 
in  series  3  provided  on  the  periphery  with  pressure  vanes  or  blades  such  as  2  (Fig.  216) 
is  revolubly  mounted  in  the  enclosing  covers  4  and  5  of  the  casing  6.  The  casing  6  is  at 


Turbine  Regulators 


r75 


one  end  wider  than  at  the  other.  The  cover  4  at  the  smaller  end  has  a  pipe  socket  for  the 
admission  of  the  steam,  the  other  cover  5  has  a  pipe  socket  for  the  escape  of  the  steam. 

The  separate  tur- 
bine bodies  3  (of  which 
there  are  five  in  the 
present  example)  lie  in 
separate  compartments 
of  the  casing,  which  are 
formed  by  partitions  7 
tight  jointed  on  the  shaft 
i.  A  larger  or  smaller 
number  of  passages 
which  are  contained  in 
these  partitions  7  may 
be  closed  by  means  of 
ring  slides  8  lying  in 
front  of  them. 

These  ring  slides  are 
provided  on  the  upper 
part  of  their  periphery 
with  teeth  9,  in  which 
toothed  segments  10 
mounted  on  shafts  n 
engage,  which  segments 
may  be  adjusted  by  FIG-  2I& — Turbine,  with  Regulator, 

means  of  a  setting  lever 

12  on  a  curved  scale  or  setting  arc  13.  The  shaft  n  passes  through  the  com- 
partments 14,  which  are  formed  by  upper  extensions  of  the  casing  6,  and  are 

tight  washered  at  one  end  by  means   of  stuffing 
boxes. 

The  guide  vanes  15  forming  the  said  passages 
are  fixed  on  the  inner  periphery  of  the  casing  6. 
Steam  flows  between  these  guide  vanes  against 
the  pressure  vanes  2  of  the  separate  turbine  bodies. 
Rods  passing  through  stuffing  boxes  on  the 
side  walls  of  the  compartments  14  so  as  to  form  a 
tight  joint,  and  provided  at  the  outer  end  with  a 
screw  thread  and  nut,  engage  above  on  the  par- 
titions 7,  in  order  to  enable  these  partitions  to  be 
also  adjusted  relatively  to  one  another  by  the 
adjustment  of  the  nuts. 

The  steam  passes  through  the  pipe  at  the  end 
4  into  the  turbines,  flows  through  these  latter  in 
the  direction  of  the  arrow,  gradually  losing  its 
force,  and  escapes  through  the  pipe  in  the  end  or 
cover  5.  Before  the  steam  can  enter  the  steam 
passages  of  the  first  ring  of  guide  vanes  it  passes 
through  the  openings  of  one  of  the  annular  slides 
8  lying  in  front  of  the  steam  passages.  The  walls 
or  plates  7  serving  as  seats  for  the  ring  slides 

have  in  the  example  shown  28  admission  openings  of  equal  section  and  equally  dis- 
tributed round  the  circle.  The  ring  slide  (Fig.  219)  has  also  28  openings  coinciding 
in  each  quarter  of  the  ring,  which  are  of  different  width  and  at  different  distances 


FIG.  219. — Turbine  Regulator. 


176 


Modern   Engines 


FlG.  220. — Schulz  Turbine  Regulator. 


apart.  The  distances  are  so  calculated  that  the  ring  slide  in  the  one  end  position, 
which  is  rendered  clear  by  the  projection  of  a  quarter  in  section  in  Fig-.  220 
(upper  Fig.),  exposes  all  the  inlet  apertures  of  the  partition  7.  When  the  annular 
disc  is  displaced  in  the  direction  of  the  arrow  (Fig.  220),  the  opening  lying  farthest 
to  the  left  of  the  wall  is  first  closed,  and  then  the  next  opening,  and  so  on  simul- 
taneously in  all  four 
quarters,  until  the  posi- 
tion shown  in  Fig.  220 
(lower  Fig.)  is  reached, 
in  which  only  one  open- 
ing of  the  wall  7  re- 
mains uncovered  in  each 
quarter.  How  many 
openings  are  closed  by 
the  ring  slides  may  be 
ascertained  on  the  scale, 
which  is  divided  into  7 

parts  on  the  setting  arc  13.  By  moving  the  setting  lever  12  to  the  extent  of  one 
section  of  the  scale,  all  the  annular  discs  8  are  so  turned  that  4  of  the  28  openings  of 
each  wall  7  are  closed. 

Another  German  engineer  is  in  the  field,  Johann  Stumpf,  Berlin,  with  a  patent 
18,952,  1902,  for  a  compound  turbine  like  Rateau's — essentially  a  number  of  De  Laval 
wheels  in  series.  Rateau 
and  Laval  turbines  are  axial 
flow  machines. 

Stumpf  affects  the  in- 
ward flow,  and  he  shows  us 
how  to  cut  off  part  of  the 
turbine  when  on  small  load 
by  stop  valves  or  slide  valves. 
This  invention  relates 
to  improvements  in  steam  or 
gas  turbines,  and  more  espe- 
cially to  a  turbine  in  which 
the  steam  is  expanded  and 
the  pressure  of  the  same 
is  transferred  into  working 
energy. 

The  object  of  this  in- 
vention is  to  so  construct  a 
turbine  that  the  number  of 
revolutions  of  the  turbine 
can  be  changed  at  will. 

The  construction  is 
shown  in  the  illustrations, 
in  which — 

Fig.  221  is  a  vertical 
section  of  a  turbine,  constructed  according  to  this  invention,  and 

Fig.  222  is  a  vertical  section  of  a  modification  of  the  turbine  shown  in  Fig.  163. 
The  invention  consists  in  so  constructing  the  turbine  that  one  or  several  turbine 
wheels  can  be  cut  out  in  such  a  manner  that  a  greater  or  smaller  number  of  turbine 
wheel  rims  come  into  action  for  effecting  the  transformation  of  the  steam  pressure  into 
energy. 


FlG.  221. — Stumpf  Turbine. 


Stumpf  Turbines  177 

The  invention  may  be  carried  out  in  different  ways  according-  to  the  construction 
of  the  turbine,  and  especially  according  to  the  circumstance  whether  the  pressure  of  the 
steam  is  utilised  in  the  turbine  in  a  series  of  turbine  wheel  rims  step  by  step,  or  whether 
the  steam  expands  in  the  first  admission  nozzle  up  to  the  exhaust  or  condenser  pressure, 
so  that  the  steam  works  only  by  its  velocity. 

In  turbines  of  the  first  mentioned  type,  one  or  several  turbine  wheels  can  simply  be 
cut  out  by  leading  the  steam  before  it  comes  to  the  last  turbine  wheel  or  turbine  wheels 
to  the  condenser  or  into  the  atmosphere.  In  turbines  of  the  latter  type  the  object  may  be 
attained  in  a  very  simple  manner  by  arranging  the  turbine  wheels  or  the  leading  vane 
rims,  so  that  the  same  can  be  shifted  sideways  in  the  direction  of  the  axis  of  the  wheels, 
so  that  the  steam,  after  having  worked  in  a  number  of  turbine  wheels,  flows  immediately 
into  the  condenser  or  into  the  atmosphere. 

Fig.  221  relates  to  the  first  type  of  turbines,  that  is,  to  a  turbine  in 
which  the  steam  expands  in  each  nozzle  step  by  step,  a1,  a2,  a3,  a*,  a5,  a?  are  turbine 
wheels  fixed  to  the  common  shaft  b.  Each  turbine  wheel  rotates  in  a  chamber 
c1,  c2,  c3,  c4,  c5,  c6  of  the  common  turbine  casing.  The  live  steam  enters  at  d  an  annular 
channel  e1,  and  streams  through  nozzles  f  upon  the  first  turbine  wheel  a1.  In  the 
example  shown  in  the  drawing,  turbine  wheels  with  double  buckets  are  shown,  so  that 
the  steam  enters  on  both  sides  of  the  turbine  wheel  into  the  chamber  c1.  The  steam 
leaving  the  turbine  wheel  on  the  right-hand  side  of  the  same  (as  shown  in  the  Figure) 
immediately  flows  through  ports  g  to  the  second  annular  channel  e2.  The  steam  turbine 
leaving  the  first  turbine  wheel  on  the  left-hand  side  flows  through  passages  passing 
through  the  ring  h  containing  the  nozzles  to  the  right-hand  side  and  flows  into  the 
second  annular  channel  e2,  the  direction  of  flow  of  the  steam  being  shown  by  the  arrows 
in  the  drawing.  From  the  annular  channel  e2  the  steam  then  impinges  upon  the  second 
turbine  wheel  a2,  and  so  on.  The  steam  leaves  the  last  chamber  c6  through  the  pipe  /, 
which  leads  to  the  condenser. 

In  the  Figure  a  special  pipe  k  for  the  annular  channel  et  is  shown,  which  pipe  is 
connected  at  kl  to  the  condenser  pipe  i.  The  pipe  k  has  a  valve  /,  and  the  pipe  i  has 
a  valve  m  between  the  turbine  casing  and  the  spot  k1  where  the  pipe  k  is  connected  to 
the  pipe  i.  If  the  valve  m  is  closed  and  the  valve  /  is  opened,  the  steam  flows  from  the 
annular  channel  £*,  that  is  to  say,  after  having  worked  in  the  first  three  turbine  wheels 
a1,  a2,  a3,  to  the  condenser.  In  the  Figure  the  annular  channel  e*  is  only  shown  con- 
nected to  the  pipe  z,  but  it  will  be  understood  that  this  connection  may  be  also  provided 
for  all  the  other  annular  channels,  so  that  each  of  the  channels  can  be  connected  directly 
to  the  condenser. 

If,  as  is  the  case  in  this  construction,  the  steam  has  to  be  passed  into  a  smaller 
number  of  turbine  wheels  than  the  total  number  contained  in  the  turbine,  owing  to  a 
reduction  in  the  pressure  of  the  steam,  it  is  natural  that,  corresponding  to  the  reduction 
of  the  pressure  of  the  steam  in  each  nozzle  system,  a  greater  cross  section  of  the 
admission  nozzles  for  the  single  wheels  must  be  obtained.  This  can  be  attained,  for 
instance,  by  cutting  out  a  number  of  nozzles  and  increasing  the  area  of  those  still  open, 
and  this  may  be  accomplished  in  any  suitable  manner,  for  instance,  by  means  of  an 
annular  slide  or  the  like. 

In  Fig.  222  the  invention  is  shown  as  applied  to  a  turbine,  in  which  the  steam 
expands  immediately  to  the  pressure  ot  the  condenser  or  exhaust,  so  that  the  whole 
pressure  is  immediately  transferred  into  streaming  velocity.  In  the  example  a  steam 
turbine  is  shown  in  which  three  turbine  wheels  d,  b1,  b'2  are  arranged  upon  a  common 
shaft  a.  The  turbine  wheel  b  situated  in  the  middle  is  provided  with  a  turbine  wheel 
rim  cy  in  which  are  arranged  the  well-known  double  buckets  after  the  manner  of  the 
Pelton  wheel  system.  The  two  outer  wheels  b1  and  b2  have  wheel  rims  dl  and  a72,  in 
each  of  which  rims  are  provided  two  rows  of  single  buckets  of,  for  instance,  a  U-formed 
cross  section.  The  steam  flows  into  the  turbine  through  an  annular  channel  e,  and 
VOL.  i. — 12 


178 


Modern   Engines 


streams  through  nozzles /to  the  double  buckets  of  the  wheel  b.  In  order  to  lead  the 
steam  from  these  buckets  to  the  additional  turbine  wheel  rims,  four  leading  vane  rims 
g1  g2  and  hl  h2  are  provided.  The  steam  jets  entering  through  the  nozzles  f  and 
impinging  upon  the  rim  c  of  the  turbine  wheel  b  are  divided  by  means  of  the  double 
buckets  into  two  parts.  These  parts  stream  through  the  buckets  and  enter  the  leading 
vane  rims^1^2,  in  which  the  streaming  direction  is  reversed,  so  that  they  enter  again  in 
the  right  direction  into  the  first  rows  of  buckets  dl  and  d2.  After  streaming  through 
these  buckets  the  streaming  direction  is  again  reversed  in  the  leading  vane  rims  kl  and 

/t2,  so  that  the  steam  is  led  into 
the  last  row  of  buckets  of  the 
turbine  wheels  b1  and  b2,  from 
where  it  enters  into  the  turbine 
casing  in  order  to  exhaust  or  to 
be  condensed. 

Several  or  all  of  the  leading 
vane  rims  g  and  h  are  movable 
sideways.  In  the  Figure  the 
leading  vane  rims  h1  and  h2  are 
provided  with  guide  pieces  kl 
and  k2,  by  means  of  which  they 
can  be  moved  sideways  in  the 
turbine  casing  z'.  The  devices 
for  moving  the  rims  may  be  of 
any  convenient  form.  In  the 
Figure,  rods  ml  and  m2  are 
shown,  the  number  of  which  rods 
is  equally  divided  up  over  the 
whole  -  circumference  of  the  re- 
spective vane  rims,  means  being 
provided  for  moving  all  the  rods 
ml  and  m2  simultaneously  by 
means  of  a  common  lever  mech- 
anism. Also  for  the  leading  vane 
rim  g2  guide  rods  o  are  shown, 
in  order  to  make  clear  that  the 
outer  as  well  as  the  inner  vane 
rims  are  movable,  either  singly 
or  both  together. 

If,  for  instance,  the  number 
of  revolutions  for  the  number  of 
turbine  wheels  and  leading  bucket 
rims  shown  in  the  drawing,  and 
for  a  diameter  of  the  turbine 


FIG.  222. — Stumpf  Turbine. 


wheels  of  3  metres,  amounts  to  500,  and  the  outer  leading  vane  rims  /z1  and  A2  are  moved 
sideways,  the  number  of  revolutions  increases  up  to  1000  for  nearly  the  same  steam 
consumption.  If,  now,  the  following  leading  vane  rims  are  moved  sideways  so  that  the 
steam  streams  out  freely  from  the  first  turbine  wheel,  the  number  of  revolutions  should 
increase  up  to  2000  in  order  to  obtain  about  the  same  steam  consumption. 

In  this  example  an  augmentation  of  the  number  of  revolutions  from  500  to  1000, 
and  from  1000  to  2000  is  attained.  Naturally,  it  is  also  possible  to  create  intermediate 
steps.  It  will  be  clear  that  the  arrangement  shown  and  described  cannot  only  be  used 
in  turbines  provided  with  double  buckets  after  the  Pelton  wheel  system,  but  that  it  may 
also  be  used  for  turbines  in  which  the  steam  jet  is  not  divided  up  into  two  parts. 


Curtis  Turbines 


179 


As  the  Curtis  turbine  is  being  pushed  forward  in  this  country  a  few  extracts  from 
some  of  his  patents  are  of  interest.  It  may  be  said  at  once  that  although  we  have  three 
voluminous  specifications  before  us  it  is  very  difficult  to  discover  much  new  to  select 
from  the  descriptions  and  illustrations.  From  one  specification,  No.  19,246,  1896,  we 
may  take  a  sample  or  two.  This  specification  has  fourteen  pages  closely  printed,  and 
elaborately  tells  us  all  over  again  what  Parsons  and  De  Laval  had  told  us  ten  years 
before,  and  Wilson  and  Pilbrow  thirty  years  before  that.  As  an  example  of  an  American 
specification  covering  some  small  detail  improvements,  it  is  difficult  to  surpass  it. 
There  are  seven  claims  and  nine  sheets  of  drawings.  A  few  illustrations  from  the  nine 
sheets  with  their  explanations  are  given  thus : — 

In  Fig.  223  is  represented  a  turbine  having  four  sets  of  movable  vanes  D,  D1, 
D2,  D3,  and  three  stationary  intermediate  passages  E,  E1,  E2,  constructed  and  operat- 
ing on  this  principle.  In  this  case,  and  assuming  that  the  apparatus  is  designed 
to  work  between  the  initial  and  terminal  pressures  before  taken  for  illustration, 
i.e.  a  boiler  pressure  of  150  Ibs.  and  an  exhaust  pressure  of  2  Ibs.  per  square  inch 
(absolute),  the  delivery  nozzle  G  will  be  proportioned  in  the  manner  described  so  as 


FIG.  223. — Curtis  Turbine. 

to  expand  the  steam  down  to  a  given  pressure,  say  10  Ibs.  at  its  discharging  end, 
the  remaining  pressure  above  the  pressure  of  the  exhaust  being  that  assumed  to 
maintain  the  flow  in  the  working  passages.  If  the  steam  jet  enters  the  exhaust  with  20 
per  cent,  of  the  original  velocity,  each  of  the  four  sets  of  movable  vanes  will  abstract 
20  per  cent,  of  the  velocity,  and  will  in  their  order  absorb  respectively  36,  28,  20,  and 
12  per  cent,  of  the  energy  represented  by  the  original  velocity,  while  4  per  cent,  of  the 
energy  will  pass  off  as  residual  velocity  in  the  exhaust.  The  decline  in  pressure  in 
the  working  passages  will  be  such  that  at  the  discharge  ends/",  f1,  and/2  of  the 
stationary  intermediate  passages  the  pressures  will  be  less  and  less,  declining  at  a 
certain  rate  which  should  be  found  by  experiment  in  each  particular  type  and  size 
of  machine,  and  owing  to  both  reduced  velocity  and  to  increased  volume  of  the  fluid  jet 
from  reduced  density  the  cross  sectional  areas  at  the  points/,/1,/2  will  be  corre- 
spondingly increased  over  the  cross  sectional  area  of  the  discharge  end  e  of  the  nozzle, 
and  over  each  other  successively.  The  expansion  in  the  working  passages  is  shown 
in  full  lines  as  taking  place  in  both  the  movable  and  stationary  passages,  while  by  the 
dotted  lines  this  expansion  is  shown  as  taking  place  wholly  in  the  stationary  passages. 
The  former  plan  is  preferable. 


i8o 


Modern  Engines 


In  Fig.  224  is  shown  an  apparatus  designed  to  have  the  same  proportions  of  the 
expanding  nozzle  and  the  working  passages  and  to  operate  under  the  same  conditions 
as  the  apparatus  of  Fig.  223.  It  has  the  peculiarity  in  construction  of  having 
the  different  sets  of  movable  vanes  mounted  upon  separate  wheels.  It  also  differs 
in  the  construction  of  the  stationary  intermediate  passages  which  will  be  presently 
described. 

Besides  the  forms  of  apparatus  which  have  been  described,  many  features  of  the 
invention  are  involved  in  the  construction  and  operation  of  such  an  apparatus  as  that 
shown  in  Fig.  225,  in  which  only  movable  vanes  are  employed  in  the  working  part  of 
the  apparatus,  the  sets  of  vanes  being  alternately  mounted  upon  oppositely  rotating 
discs,  and  delivering  the  fluid  jet  from  one  set  of  movable  vanes  directly  to  another 
set  without  the  interposition  of  stationary  passages.  It  will  be  understood  that  the 
movable  vanes  have  all  the  characteristics  of  the  movable  vanes  already  described, 

but  that  those  on  one  disc  are 
set  or  curved  oppositely  to  those 
on  the  other  disc.  In  the  appa- 
ratus illustrated  in  Fig.  226  the 
expanding  nozzle  is  designed  to 
convert  all  or  the  larger  portion 
of  the  useful  pressure  into  vis 
viva,  although  the  overlapping  of 
the  operations  of  converting  pres- 
sure into  vis  viva  and  vis  viva 
into  mechanical  power  can  like- 
wise be  employed  in  an  apparatus 
of  this  kind. 

It  will  be  observed  that  in  all 
forms  of  the  apparatus  the  steam 
or  other  elastic  fluid  is  delivered 
to  the  working  passages  prac- 
tically in  the  form  of  a  solid 
stream  or  "jet,"  whose  cross 
sectional  area  is  large  compared 
with  its  perimeter,  and  that  this 
jet  acts  at  one  time  only  on  a 
small  section  of  the  vanes  of  a 
circular  range.  This  arrange- 
ment has  a  great  practical  ad- 
vantage over  one  wherein  the  fluid  is  delivered  in  the  form  of  an  annular  film  simul- 
taneously to  all  the  vanes  of  a  complete  circular  range.  In  the  latter  arrangement,  in 
order  to  reduce  the  total  cross  section  of  the  passage  to  that  required  and  still  have 
the  proper  velocity,  the  depth  of  the  vanes  has  to  be  exceedingly  small,  and  the  surface 
exposed  to  the  flowing  fluid  is  very  large  compared  with  the  cross  sectional  area  of 
the  passages.  The  result  is  great  loss  by  surface  friction  and  churning  action,  and  in 
addition  the  clearance  space  is  so  extended  that  it  becomes  large  in  proportion  to  the 
area  of  the  passages. 

Whether  the  turbines  are  now  made  on  these  principles  and  designs  we  cannot 
ascertain,  but  large  turbines  of  some  kind  or  another,  the  leading  feature  of  them  being 
that  they  have  vertical  shafts,  are  being  placed  on  the  market. 

On  the  whole,  it  will  be  seen  from  all  this  that  very  little  has  been  contributed  to 
the  improvement  of  steam  turbines  by  any  specification  other  than  De  Laval  and 
Parsons.  Arrangements  for  governing  and  regulating,  placing  turbines  side  by  side, 
or  end  to  end,  or  one  inside  the  other,  forming  vanes,  nozzles,  and  jets,  constructing 


FIG.  224. — Curtis  Turbine. 


Curtis  Turbines 


181 


wheels  for  high  velocity,  yielding1  bearings  and  flexible  shafts  are  subjects  upon  which 
inventors  and  patent  agents  have  been, 
and  no  doubt  will  continue,  ringing  the 
changes  for  some  time  to  come. 

STEAM  TURBINE  TESTS 

It  is  necessary  here  to  give  some 
results  of  steam  turbine  tests  to  form 
some  idea  of  their  practical  perform- 
ances. Some  tests  we  have  briefly  re- 
ferred to  already,  so  that  we  may  select 
only  a  few  typical  ones.  We  shall  have 
occasion  in  future  volumes  to  refer  to 
their  special  performances  in  connection 
with  the  work  to  which  they  are  applied 
— marine  propulsion,  pumps,  fans,  and 
dynamos.  Parsons  and  De  Laval  tur- 
bines are  the  only  ones  at  this  date 
upon  which  reliable  independent  tests 
have  been  reported,  so  that  we  are 
unable  to  give  results  for  the  later 
turbines. 

Up  till  1890  Parsons  turbines  had 
not  been  made  condensing,  but  were 
chiefly  of  small  sizes  for  electric  light- 
ing, as  we  have  seen  from  the  patents.  FlG.  225._Curtis  Turbine. 

The  next  step  in  advance  was  the 
construction  of  an  experimental  steam  turbine  of  200  horse-power  in  1892.  It  was  coupled 


FIG.  226. — Fixed  and  Movable  Blades  of  Curtis  Turbine. 
to  a  loo-kilowatt  alternator,  and  supplied  with  moderately  superheated  steam  at  100  Ibs 


182 


Modern  Engines 


pressure  per  square  inch.  When  tested  by  Professor  J.  A.  Ewing,  F.R.S.,  it  was  found 
to  consume  27  Ibs.  steam  per  kilowatt-hour,  thus  rivalling-  the  performances  of  the  best 
compound  condensing  reciprocating  engines.  This  result  placed  the  steam  turbine  amongst 
the  most  economical  means  of  obtaining  electrical  energy  from  steam,  and  led  to  its 
adoption  in  the  lighting  stations  of  Newcastle,  Scarborough,  Cambridge,  and  other  places. 

About  two  years  later  considerable  alterations  of  design  and  workmanship  were 
introduced  ;  a  single  flow  type  of  parallel  flow  turbine  having  been  adopted  instead 
of  the  original  double  flow  with  right-  and  left-handed  turbines  on  each  side  of  the 
steam  inlet,  the  second  set  of  turbines  were  replaced  by  rotating  steam  balance  pistons, 
and  the  steam  passed  in  one  direction  parallel  to  the  shaft.  This  alteration  materially 
improved  the  economy  and  reduced  the  amount  of  skilled  labour  required.  The  form 
and  construction  of  the  vanes  or  blades  was  perfected  and  strengthened,  and  many 
minor  improvements  conducive  to  economy  were  made,  so  that  even  in  the  smaller 
sizes  a  fair  degree  of  efficiency  has  been  obtained,  as  is  instanced  by  the  result  ot 
28.8  Ibs.  of  steam  per  kilowatt-hour,  or  about  17  Ibs.  per  indicated  horse-power,  for 
a  24-kilowatt  steam  turbine  plant  without  superheat. 

The  following  tables  will  give  the  general  results  of  reliable  tests  on  Parsons' 
turbines : — 

TABLE  XVII.— TEST  OF  24-KILOWATT  TURBO  DYNAMO  FOR  MESSRS.  SPILLERS  & 

BAKERS,  NEWCASTLE-ON-TYNE. 


Pressure  of 

Vacuum 

Steam  above 

Superheat 

in  the 

Revolutions 

Atmosphere 

at  Stop 

Turbine 

per 

Load. 

Steam  used. 

at  Stop 

Valve. 

Cylinder. 

Minute. 

Valve. 

Bar.  =  30". 

Lbs.  per 
Square  Inch. 

F.° 

Inches  of 
Mercury. 

Kilowatts. 

Lbs.  per 
Hour. 

Lbs.  per 
Kw.-hour. 

80 

o 

28.8 

499° 

24.7 

712 

28.8 

77 

o 

29.0 

4630 

11.8 

400 

33-9 

74 

o 

29.1 

4570 

5-i5 

^      235 

45-6 

78 

o 

26.0 

4900 

23.8 

798 

33-5 

79 

o 

o 

4780 

19.7 

X35° 

68.5 

The  increase  of  efficiency  with  better  vacuum  is  well  shown  here.  With  28.8  inches 
vacuum  this  is  about  4.6  Ibs.,  or  16  per  cent.,  better  than  with  26  inches  vacuum. 

A.  5o-kilowatt  steam  turbine  alternator  for  the  Corporation  of  Blackpool  showed  a 
consumption  of  28  Ibs.  per  kilowatt-hour  at  full  load  without  superheat. 


TABLE  XVIIL— 50-KILOWATT  STEAM  ALTERNATOR  FOR  THE  BLACKPOOL 

CORPORATION. 


Pressure  of 
Steam  above 
Atmosphere 
at  Stop 
Valve. 

Superheat 
at  Stop 
Valve. 

Vacuum 
in  the 
Turbine 
Cylinder. 
Bar.  =30". 

Revolutions 
per 
Minute. 

Load. 

Steam  used. 

Lbs.  per 
Square  Inch. 
126 

•  o 

Inches  of 
Mercury. 
28.0 

5°44 

Kilowatts. 
52.7 

Lbs.  per 
Hour. 
1480 

Lbs.  per 
Kw.-hour. 
28.0 

132 

o 

28.5 

4880 

o 

320 

The  above  shows  the  results  on  small  turbines. 


Steam  Turbine  Tests 


For  larger  powers  and  with  superheat  the  results  are,  of  course,  much  better,  as 
the  following  table  shows  : — 

TABLE  XIX.— VARIOUS  soo-KILOWATT  TURBO  ALTERNATORS. 


Pressure  of 
Steam  above 
Atmosphere 
at  Stop 
Valve. 

Superheat 
at  Stop 
Valve. 

Vacuum 
in  the 
Turbine 
Cylinder. 
Bar.  =  30". 

Revolutions 
per 
Minute. 

Load. 

Steam  used. 

SCARBOROUGH  ELECTRICAL  SUPPLY  COMPANY. 

Lbs.  per 
Square  Inch. 

F.° 

Inches  of 
Mercury. 

Kilowatts. 

Lbs.  per 
Hour. 

Lbs.  per 
Kw.-hour. 

126 

o 

26.75 

2400 

529 

22.7 

12,023 

128 

o 

27.7 

»» 

258 

26.4 

6,812 

164 

0 

28.1 

2600 

o 

... 

1.477 

CHELTENHAM  CORPORATION. 

130 

0 

26.7 

3000 

553 

21.7 

12,000 

130 

o 

26.6 

,» 

278 

26.2 

7,280 

i33 

o 

24.0 

,» 

553 

23.6 

13,060 

130 

o 

»> 

ii 

453 

24.8 

11,250 

J35 

0 

» 

» 

276 

29.65 

8,i75 

BLACKPOOL  CORPORATION. 

146 

70 

27.1 

2500 

5i5 

21-35 

11,000 

150 

o 

27.0 

502 

23.1 

11,600 

i35 

o 

27-3 

497 

24.0 

",953 

i33 

66 

27-3 

5°7 

21.  1 

10,693 

152 

o 

29.0 

0 

1,500 

160 

0 

23.6 

o 

2,530 

156 

5 

28.9 

o 

1,465 

It  will  be  noted  from  the  above  results  that  the  improvement  in  steam  consumption 
resulting  from  a  superheat  of  50°  F.  is  about  8  per  cent.,  and  from  100°  F.  it  averages 
about  12  per  cent.  ;  also  that  for  every  inch  of  vacuum  above  25  inches  or  26  inches  the 
consumption  of  steam  falls  about  4  per  cent. 

It  will  be  noted  that  in  steam  turbines  the  steam  consumption  closely  follows  a  right 
line  law,  or  is  proportional  to  the  load  plus  a  constant  quantity  which  represents  the 
consumption  of  steam  at  no  load. 

In  connection  with  superheated  steam  it  may  be  mentioned  that,  as  there  is  no 
internal  lubrication  of  the  turbines,  none  of  the  usual  difficulties  which  occur  with 
reciprocating  engines  are  met  with  in  its  employment. 

Also,  in  steam  turbines  the  absence  of  internal  lubrication  renders  the  exhaust  steam 
absolutely  free  from  oil,  so  that  the  water  from  the  hot  well  can  be  returned  to  the  boilers 
direct  without  oil  filters. 

Special  tests  have  been  made  from  time  to  time  on  turbine  engines  to  verify  the 
statement  that  no  increase  in  steam  consumption  occurs  with  the  age  of  the  plant  under 
fair  wear  and  tear. 

As  to  the  consumption  of  steam  on  still  larger  plants,  a  long  and  exhaustive 
series  of  tests  was  made  in  January  1900  by  Mr.  W.  H.  Lindley  and  Professors 
Schroter  and  Weber,  on  behalf  of  the  city  of  Elberfeld  in  Germany,  on  one  of  two 
1000- kilowatt  turbo  alternators  built  at  Heaton  Works  for  that  city.  The  turbo 
alternators  were  constructed  to  give  1500  kilowatts  at  4000  volts  50  periodicity, 
the  alternators  being  four  pole  running  at  1500  revolutions  per  minute,  and  directly 
coupled  to  the  turbines.  The  expansion  of  the  steam  was  carried  out  in  two  cylinders, 
a  high  pressure  and  a  low  pressure,  the  steam  being  expanded  down  to  a  little  below 


184 


Modern  Engines 


the  atmosphere  in  the  first,   and  from  that  to  the  vacuum  of  the  condenser  in  the 
second. 

We  have  not  space  here  to  refer  to  the  modus  operandi  of  these  tests,  nor  all  the 
results.     A  summary  of  them  will  suffice. 

TABLE  XX. 


•O 

-o^  E 

£1 

£°  [j 

fe  °l  ^ 

&>-£ 

S  <B  c 

QJ     CO       • 

*n  2l  w 

CJ    ^  ^5  ^^ 

.  ^       • 

«  a  5 

_n    <5  *•" 

C    3C/3 

_S    3  T3  ^5 

"rt  "3 

C/3  0  J3 

Load. 

O-i  "o 

4J  £ 

111 
j|j 

O  nl  ^ 
p  (U  o3  o 

Sil! 

4)  O 

•eX 

IU 

a-; 

3    0 

!'f! 

a>  3;  _o 

< 

UH^ 

^Hc£ 

Oo 

(O 

(2) 

(3) 

(4) 

(5) 

(6) 

Kilowatts. 

Kgs.  per 
cm?. 

C.° 

C." 

C.' 

Kgs. 

1190.  i 

IO.  II 

179-3 

189.5 

IO*2 

8.81 

994.8 

10.47 

180.9 

192.0 

II.  I 

9.14 

745-3 

10.76 

182.0 

190.0 

8.0 

IO.  12 

498.7 

10.40 

180.6 

209.7 

29.1 

11.42 

246.5 

10.14 

179.4 

196.4 

17.0 

15.31 

No  load  withl 
excitation.     J 

10.34 

180.3 

193.0 

13-3 

per  hour. 
1844 

No  load  with-\ 
out  excitation.  / 

10.49 

181.0 

194-5 

13-5 

1183 

For  the  following  outputs  in  round  numbers  the  steam  consumption  per  hour  is  as 
shown : — 

TABLE  XXI. 


Output. 

Steam  Consumption 
per  Hour. 

Steam  Consumption 
per  Kilowatt-hour. 

Kilowatts. 

Kilogrammes. 

Kilogrammes. 

1250 

10,786 

8.63 

1OOO 

9,189 

9.19 

750 

7.496 

9.99 

500 

5.707 

11.41 

250 

3,821 

15.28 

On  the  second  plant,  tests  were  made  to  determine  the  advantages  of  superheating, 
and  also  the  effect  of  varying  the  vacuum. 


TABLE  XXII. 


Pressure  Stop 
Valve. 

Superheat. 

Vacuum. 
Bar.  =30". 

Kilowatts. 

Steam  per 
Kilowatt-hour. 

Lbs.  per  Square  Inch. 
J57-5 
153 
125 

C.° 
o 
o 
o 

Inches  of  Mercury. 
26.97 

24-45 
27.10 

IOIO 

1041 

IO22 

Lbs. 
23.08 

25-25 
20.47 

These  show  a  gain  of  about  12  per  cent,  with  55°  C.  superheat,  and  that  every  inch 
of  vacuum  improves  the  consumption  about  4  per  cent. 


Steam  Turbine  Tests 


In  non-condensing  plants  also  many  tests  have  been  made,  but,  as  will  be  expected, 
the  steam  turbine  compares  rather  more  favourably  with  the  reciprocating1  engine  in  con- 
densing types.  In  a  ico-kilowatt  size  a  consumption  of  39  Ibs.  per  kilowatt-hour  has 
been  attained,  and  in  a  25o-kilowatt  turbo  dynamo  38  Ibs.  per  kilowatt-hour,  both  with 
about  130  Ibs.  steam  pressure  and  no  superheat. 

In  larger  sizes  of  1500  kilowatts,  with  200  Ibs.  steam  pressure  and  150°  F.  superheat, 
a  consumption  of  28^  Ibs.  per  kilowatt-hour  non-condensing  has  been  guaranteed,  and  is 
expected  to  be  easily  attained,  if  not  surpassed. 

At  the  discussion  of  these  results  at  the  International  Congress  in  Glasgow,  1901, 
Mr.  Gerald  Stoney  added  the  following  interesting  remarks.  He  said  :  "  Tests  made  on 
turbines  which  have  been  running  for  a  long  time  showed  that  there  was  no  falling  off 
of  economy.  With  reference  to  superheat,  a  small  degree  of  superheat  gave  about  5  to 
6  per  cent,  extra  economy  :  50°  F.  8  per  cent.,  and  100°  F.  12  per  cent.  No  tests  had 
been  made  at  higher  degrees  of  superheat,  but  there  was  no  doubt  the  economy  would 
increase  with  higher  superheats,  and  would  probably  reach  20  per  cent,  with  350°  F. 
There  was  no  difficulty  in  working  with  any  degree  of  superheat  the  superheater  would 
stand.  The  effect  of  a  good  vacuum  was  felt  more  in  the  steam  turbine  than  in  an 
ordinary  engine,  as  it  expanded  right  down  to  the  vacuum  of  the  condenser,  which 
is  not  possible  in  an  ordinary  engine.  In  relation  to  the  consumptions  of  ordinary 
engines  and  turbines  at  Elberfeld,  where  both  were  installed  in  the  same  station  and 
therefore  were  tested  under  the  same  conditions,  the  consumption  of  the  steam  turbines 
from  three-quarters  to  full  load  was  better  than  that  of  the  Sulzer  triple-expansion 
engines." 

These  large  plants  are  shown  in  Plate  VII.,  where  the  high  pressure  and  intermediate 
pressure  turbines  are  at  the  left-hand  side  in  one  casing.  The  low  pressure  turbine  is 
shown  at  the  middle,  with  a  bearing  between  it  and  the  first  two.  Then  comes  another 
bearing,  and  beyond  that  the  alternator  and  a  small  exciter. 

The  turbines  of  Mr.  Parsons  were  tested  on  the  ship  Turbinia  by  Professors  Ewing 
and  Dunkerly  for  steam  consumption.  For  first  trial  purposes  the  T^^rb^n^a  was  con- 
structed— her  dimensions  being  100  feet  in  length,  9  feet  beam,  3  feet  draught  of  hull, 
and  44  tons  displacement.  She  was  fitted  with  turbine  engines  of  2000  actual  horse- 
power, with  an  expansive  ratio  of  i5o-fold,  also  with  a  water-tube  boiler  of  great  power, 
of  the  express  small  tube  type,  but  with  no  feed  heater.  The  turbine  engines  consisted 
of  three  separate  turbines — the  high  pressure,  the  intermediate,  and  the  low  pressure — 
each  driving  one  screw  shaft  independently  ;  to  the  low  pressure  or  centre  shaft  the 
reversing  turbine  was  also  coupled,  and  on  each  shaft  were  keyed  three  propellers  of 
small  diameter  and  of  normal  pitch  ratio.  This  arrangement  was  found  to  be  the  best 
after  many  trials,  and  has  since  been  adhered  to  in  subsequent  vessels.  The  maximum 
indicated  horse-power  that  has  been  obtained  on  runs  of  about  5  miles'  duration  has  been 
2300,  giving  a  speed  of  34^  knots  ;  but  a  speed  of  31  knots  can  be  maintained  for  about 
2  hours'  duration,  and  as  recently  as  last  August  runs  at  this  speed  were  made  at  Havre 
for  the  Committee  of  the  Paris  Exhibition,  the  vessel  at  the  time  being  heavily  laden 
and  with  a  foul  bottom,  showing  that  after  four  years  of  work  the  turbine  engines  do  not 
deteriorate  in  efficiency.  Since  she  was  completed  she  has  run  several  thousand  miles, 
sometimes  in  very  heavy  seas,  and  the  main  engines  have  never  caused  a  moment's 
anxiety,  nor  have  any  repairs  to  them  been  required. 

The  tests,  which  occupied  more  than  a  fortnight,  were  very  elaborate,  and  com- 
prised feed-water  measurements,  of  great  accuracy,  at  various  speeds  up  to  31  knots. 
The  water  measurements  were  made  by  meters  which  were  calibrated  before  and  after 
each  day's  running.  At  the  higher  rates  of  speed  two  meters  were  placed  in  series 
so  as  to  check  each  other ;  the  errors  as  determined  by  the  calibration  were  less 
than  2|  per  cent.,  and  the  results  were  taken  as  accurate  within  less  than  this 
amount. 


1 86  Modern  Engines 

The  horse-power  was  determined  by  model  experiments  in  one  of  the  principal  test- 
ing1 tanks  in  this  country. 

At  the  speed  of  31  knots  the  consumption  of  steam  for  all  purposes  was  deter- 
mined to  be  14^  Ibs.  per  indicated  horse-power,  the  coefficient  of  propulsive  horse- 
power to  indicated  horse-power  being  taken  at  55  per  cent.  In  other  words,  the 
consumption  of  coal  for  all  purposes  with  a  good  marine  boiler,  under  ordinary 
conditions  and  mild  forced  draught,  would  be  less  than  2  Ibs.  per  indicated  horse-power 
per  hour. 

The  vessel's  reversing  turbine,  which  operated  the  centre  screw  shaft  only,  gave  her 
an  astern  speed  of  6£  knots,  and  when  running  at  a  speed  of  30  knots  she  could  be 
brought  to  rest  in  36  seconds.  It  was  also  found  that  she  could  be  brought  from  rest 
up  to  a  speed  of  30  knots  in  40  seconds. 

In  these  tests  the  indicated  horse-power  is  given,  but  it  is  difficult  to  estimate  this 
indicated  power  in  turbines. 

That  such  a  small  vessel  could  be  fitted  with  power  equal  to  2000  actual  horse-power 
strikingly  shows  the  small  bulk  of  such  a  marine  turbine  plant. 

The  De  Laval  tests  were  made  by  Messrs.  Erick  Andersson,  Karl  Wallin,  and  Axel 
Estelle,  Stockholm. 

The  turbine  dynamo  with  which  the  trial  took  place  was  provided  with  a  centrifugal 
pump  coupled  to  the  turbine,  and  worked  directly  from  one  of  the  inductor  shafts.  This 
pump,  at  a  suction  height  of  14  feet  9  inches,  forced  the  water  at  a  pressure  of  11.5  Ibs. 
per  square  inch  through  an  ejector  condenser. 

The  turbine  dynamo  was  placed  close  to  the  boiler  used  during  the  trial.  The  steam 
pipe  leading  to  the  turbine  was  provided  with  a  water  strainer. 

The  boiler,  which  was  tubular  and  provided  with  an  inside  furnace,  was  fed 
with  water  at  a  temperature  of  43°  Fahr.,  and  generated  steam  at  118  Ibs.  per 
square  inch,  which  was  reduced,  however,  to  114  Ibs.  by  the  throttle  valve  of  the 
governor. 

The  trial  lasted  eight  hours  without  interruption,  and  the  fuel  used  was  "  Best  South 
Yorkshire  Steam  Coal,"  of  which  1472  Ibs.  were  consumed  during  the  trials,  while  the 
steam  consumption  amounted  to  9823  Ibs.,  consequently  the  ratio  of  evaporation  was 

- — 3  =  6.67.     The  vacuum  was  i1?  Ibs. 
1472 

The  temperature  of  the  condensing  water  was  raised  by  the  steam  from  34°  to  50° 
Fahr.,  consequently  the  quantity  of  condensing  water  may  be  estimated  at  about  66 
times  the  quantity  of  steam,  or  1271  cubic  feet  per  hour. 

The  dynamo  developed  during  the  whole  trial  an  average  electrical  force  of  113.4 

volts  x  324.0  amperes,  or  •II3'4  x  324-°>  equai  to  49.92  electrical  horse-power,  while  the 

736 
number  of  revolutions  of  the  inductors  was  1506. 

Hence  the  result  of  the  trial  gave  a  steam  consumption  of  ^-§ — —  =24.5  Ibs.  per 

hour  per  electrical  horse-power. 

To  ascertain  the  steam  consumption  at  varying  loads  Andersson  and  Wallin  made 
a  second  trial  on  the  4th  March  in  the  following  manner : — 

1.  With  the  same  steam  pressure,   114  Ibs.,  at  the  nozzle  case — i.e.  in  the  space 
between  throttle  valve  of  the  governor  and  the  steam  nozzles — as  on  I5th  February,  and 
with  all  of  the  six  steam  nozzles  in  their  places,  the  turbine  dynamo  was  worked,  and 

developed  an  electrical  power  of  113  volts  x  326  amperes,  or  — ^ — -^ —  =  50.05  electrical 

73° 

horse-power,  consequently  the  conditions  were  as  nearly  as  possible  the  same  as  at  the 
previous  trial. 

2.  Then  one  of  the  steam  nozzles  was  taken  out  and  inserted  into  a  separate  steam 


Steam  Turbine  Tests 

pipe  leading  from  the  nozzle  case  to  a  vessel  containing  a  quantity  of  water,  the  weight 
of  which  had  been  ascertained.  The  vessel  was  placed  on  a  sensitive  balance,  so  that  any 
increase  in  weight  could  immediately  and  accurately  be  ascertained.  With  the  same 
steam  pressure  as  in  Sec.  i  the  turbine  dynamo  was  driven  with  five  steam  nozzles, 
developing  an  electrical  effect  of  113.5  volts  x  264.2  amperes,  equal  to  an  average  of 
40.74  electrical  horse-power.  At  the  same  time  the  stream,  which  during  12  minutes 
rushed  through  the  nozzle  mentioned  above,  was  condensed  and  was  found  to  be  40.5 

Ibs.,  or  per  hour  —  x  40.5  =  202  Ibs. 

12 

At  the  end  of  the  trial  all  of  the  nozzles  were  carefully  measured  and  found  to  be  of 
exactly  the  same  cross  section,  consequently  the  quantity  of  steam  which  passed  through 
them  was  6x202  Ibs.  =  1212  Ibs.  per  hour.  If  the  steam  consumption  in  Sec.  i  is 

1 2  I  2 

calculated  at  the  same  rate  the  result  is =  24.2  Ibs.  per  hour  per  electrical  horse- 

50-05 

power,  which  differs  so  very  little  from  the  result  at  the  trial  on  i5th  February  during 
8  hours,  but  the  trifling  difference  may  be  owing  to  a  slight  variation  in  taking  obser- 
vations. 

As  the  turbine  dynamo,  with  five  steam  nozzles  open,  developed  an  electrical  effect  of 
40.79  horse-power,  and  the  calculated  steam  consumption  was  5x202=1010  Ibs.  per 
hour,  in  this  case  the  quantity  of  steam  per  hour  per  electrical  horse-power  would  be 

1010  ,.  ,, 

— •  =  24.76  Ibs. 

40.79 

3.  At  this  test  2  of  the  steam  nozzles  were  closed,  while  the  steam  pressure  remained 
the  same,  namely,  114  Ibs.     The  turbine  dynamo,  with  three  steam  nozzles  opened,  now 
developed  an  electrical  power  of  113.5  volts  x  140.8  amperes,  equal  to  21.72  electrical 
horse-power,  while  the  steam  consumption,  calculated  at  the  same  rate  as  in  the  previous 
case,  was  3  x  202,  equal  to  606  Ibs.  per  hour,  or  per  electrical  horse-power  per  hour 

606 

,  equal  to  27.9  Ibs. 

21.72 

4.  The    turbine   dynamo   was    then    driven   with    four   steam   nozzles   open,    and 
the    electrical    load   was    regulated    to    113.5   volts  x  164.3    amperes,    equal    to   25.34 
electrical    horse-power,    the   steam   pressure   being   reduced   by   the   throttle   valve   of 
the   governor   to    93.8   Ibs.,    with   a  vacuum   of   13.27   Ibs.      The   quantity   of  steam 
consumed  was  measured  in  the  same  manner  as  in  Test  II.,  and  was  found  to  be 
174.2  X4,  equal  to  696.8  Ibs.  per  hour,  consequently  per  hour  per  electrical  horse-power 

_5_J_,  equal  to  27.49  IDS- 
25-34 

5.  One   of  the   steam    nozzles   was    next    closed,    so   that,    as   in   Test   III.,  the 

turbine  dynamo  was  driven  with  three  steam  nozzles  open,  and  the  electrical  load 
regulated  down  to  113.5  volts  x  83. 5  amperes,  equal  to  12.87  electrical  horse-power, 
when  the  steam  pressure  was  reduced  to  74  Ibs.,  with  a  vacuum  of  13.5  inches. 
On  measuring  the  quantity  of  steam  consumed  it  was  found  to  be  137.28x3  =  411.84 

Ibs.   per   hour;    consequently  per   hour   per   electrical   horse -power  ^  L_ L_4,    equal   to 

32.0  Ibs. 

In  the  tests  with  the  300  horse-power  turbine  the  steam  was  superheated, — in  the 
first  case  about  60°  Fahr.,  and  in  the  latter  about  20°  Fahr.  It  is  evident  that  super- 
heating is  advantageous  to  the  turbine,  as  it  gives  the  steam  jet  a  higher  velocity  and 
thus  increases  the  kinetic  energy  of  the  steam,  and  it  also  diminishes  the  resistance  of 
the  turbine  wheel,  as  illustrated  by  Table  XXIV. 

The  use  of  superheated  steam  in  connection  with  turbines  has  become  more  general 
in  recent  years.  Practically  any  degree  of  superheating  can  be  used,  as  the  highly 
heated  steam  does  not  come  into  contact  with  the  moving  parts  of  the  machinery  ;  by 


i88 


Modern   Engines 


the  time  the  steam  reaches  the  chamber  in  which  the  turbine  wheel  revolves  it  has 
already  the  pressure  and  temperature  of  the  exhaust  steam. 


TABLE  XXIII.— RESULTS   OF  TESTS  WITH   DE   LAVAL  STEAM   TURBINES 

AT   DIFFERENT  LOADS. 


Pressure 

Lbs.  of 

Turbine  Machine. 

of  Admis- 
sion Steam. 
Lbs.  per 
Square 

Vacuum 
Inches  of 
Mercury. 

No.  of 
Nozzles 
open. 

Electrical 
Horse- 
power. 

Steam  per 
Electrical 
Horse- 
power 

Remarks. 

Inch. 

per  Hour. 

50    horse-power    turbine  f 
dynamo. 
The  test  made  in  April") 
1895-                              I 

113.8 
113.8 

93-9 
74.0 

26.3 
26.3 
26.9 
27.5 

6 

5 
4 
3 

49-4 
40.2 
25.0 
12.7 

24.6 
25.2 
27-9 
32-5 

}    Work  for 
Vcondensing 
j  included. 

100  horse-power  turbine  ( 
dynamo. 
The  test  made  in  June  j 
1897.                            I 

103.7 
103.8 
107.4 
106.7 

25-8 
26.4 
26.8 
27.9 

5 
3 

2 
I 

92.7 
55-6 
35-° 
15-5 

22.6 
22.7 
24.7 
27.8 

}    Work  for 
Vcondensing 
not  included. 

Lbs.  of 

Brake 

Steam  per 

Horse- 

Brake 
Horse- 

power. 

power 

per  Hour. 

t 

113.8 

26.4 

7 

163.0 

17.6 

i 

150  horse-power  turbine 

116.9 

25-9 

6 

138.4 

18.2 

Work  for 

motor. 
The  test  made  in  Nov- 
ember 1897. 

113.8 

"4-3 
112.4 

26.2 
26.5 
27.0 

5 
4 
3 

"4-5 
88.3 
64.1 

17.9 
18.7 
19.0 

•condensing1 
not  included. 

116.2 

25-7 

2 

37-5 

22.3 

- 

192.7 

27-3 

7 

303-6 

14.1 

300  horse-power  turbine 
motor. 
The  test  made  in  De-^ 
cember  1899. 

196.3 
196.3 
196.3 
190.6 
196.3 

27.6 
27.6 
27.6 
27.8 
28.1 

6 

5 
4 
3 

2 

255-5 
216.9 
172.6 

121.  6 

74-2 

14.7 
14.4 

J4-5 
14.9 
17.2 

Work  for 
condensing 
not  included. 

2I3-3 

28.5 

I 

3i-5 

21.6 

; 

126.6 

26.98 

8 

337-45 

15.68 

300  horse-power  turbine 
motor. 
The  test  made  in  June 

IQOO 

126.4 
125.0 
125.0 
125.0 

26.99 
27.24 
27.62 
27.91 

7 
6 

4 
3 

293-7 
249.1 
162.7 
118.9 

'5-76 
15-92 
16.25 
16.70 

Work  for 
•  condensing 
not  included. 

125.0 

28.16 

2 

73-5 

18.00 

125.0 

28.25 

I 

30.4 

21.77 

From  the  results  of  trials  it  is  obvious  that  not  only  the  steam  consumption  but  also 
the  heat  consumption  (in  thermal  units  per  horse-power  per  hour)  sinks  with  increasing1 
superheating-.  With  constant  peripheral  speed  of  the  turbine  wheel  and  increasing 
superheating  the  impact  is  increased  on  account  of  the  higher  velocity  of  the  steam  ;  but 
this  loss  is  instantly  transformed  into  heat,  which  raises  the  temperature  of  the  exhaust 
steam  and  thus  diminishes  the  resistance  of  the  turbine  wheel. 

It  has  been  seen  that  in  the  construction  of  the  De  Laval  steam  turbine  it  is 
necessary  to  adopt  a  very  high  speed  of  the  principal  driving  part  of  the  machine.  This 
speed  is  afterwards  reduced  in  the  machine  by  means  of  gearing,  so  that  the  turbine  can 
be  coupled  to  ordinary  machinery. 


Steam  Turbine  Tests 


189 


TABLE   XXIV.— TESTS  WITH   A  30   HORSE-POWER   STEAM   TURBINE   WORKING   WITH 
SATURATED   AND   SUPERHEATED   STEAM    RESPECTIVELY. 

NON-CONDENSING — Steam  pressure,  7  atmospheres  absolute  =  88. 2  Ibs.     Speed  01  driving  shaft, 
2000  revolutions  per  minute.     Speed  of  turbine  wheel,  20,000  revolutions  per  minute. 


Half  Load. 

Full  Load. 

Saturated 
Steam. 

Superheated 
Steam. 

Saturated 
Steam. 

Superheated 
Steam. 

Temperature  of  the  f  Cen%rade   •        •        • 
Steam  .         .        .[Fahrenheit    .        .        . 

164 
327 

460 
860 

164 
327 

500 
932 

f  Metrical    brake   horse- 
Power  developed     .  J  E££™  ^    ^^ 
V,     power         .         .         . 

21.4 

21.  1 

24-5 
24.2 

44.1 
43-5 

Si-9 
51.2 

Steam    consumption  (Kilogrammes  per  metri- 
per   brake    hSrse  J  ,  £al  b.rak,e  h°rse-power 
,               I  Lbs.  in  English  brake 
power  per  hour     .[    horse_pow*r       .         . 

21.6 
48.3 

14.1 
3i-5 

17.7 
39-6 

"•5 

25-7 

Heat  consumption  per  metrical  brake  horse- 
power per  hour  in  metrical  heat  units 

I4,l6o 

11,270 

11,610 

939° 

Temperature  of  ex-  [Centigrade  .        .        . 
hausted  steam       .|Fahrenheit   .         .         . 

IOO 
212 

3°9 

588 

IOO 
212 

343 
649 

The  combination  of  the  De  Laval  turbine  to  other  classes  of  machinery  is  receiving" 
consideration,  yet  experiments  in  this  line  are  not  sufficiently  advanced  that  these 
machines  can  be  put  on  the  market. 

The  De  Laval  type  of  turbines  excel  in  smaller  units,  while  the  Parsons'  types  are 
essentially  large  power  machines,  and  it  is  significant  that  NEW  turbines  are  made  of 
large  units  before  any  public  tests  are  given. 

Small  steam  engines  of  any  kind  are  disappearing  before  the  gas  and  oil  engines,  so 
that  the  prospect  before  steam  engines  is  for  large  units  in  which  they  can  at  present 
compete  against  the  internal  combustion  engine. 

There  is  no  doubt  the  steam  turbine  has  given  a  new  lease  of  life  to  steam  as  a 
power  working  fluid,  and  that  they  will  altogether  supersede  the  reciprocating  engine 
for  all  purposes  where  steam  is  used  is  beyond  any  doubt  now. 

And  all  indications  point  to  the  culmination  of  all  the  improvements  in  heat  engines 
in  the  evolution  of  an  internal  combustion  turbine. 

Attempts  have  been  made  towards  this  desirable  end.  Mr.  Parsons  in  his  original 
patent  proposes  an  internal  combustion  turbine. 

Mr.  Ferranti,  in  Specification  No.  2565,  1895,  proposes  the  same  thing.  A  brief 
description  from  this  specification  will  show  the  nature  of  the  proposal : — 

In  one  development  of  the  invention  air  is  used  and  compressed  by  means  of 
pumps  through  a  chamber  lined  with  refractory  material  and  capable  of  standing  con- 
siderable pressure  which  contains  the  combustible,  preferably  in  the  form  of  coal ;  the 
working  fluid  then  becomes  heated  air,  and  the  products  of  combustion  leaving  the  fire 
chamber  at  a  very  high  temperature  and  expanding  through  expansion  tubes  so  acquire 


Modern  Engines 


190 

the  necessary  velocity  and  diminish  in  temperature  accordingly.     The  working  fluid  is 
then  used  in  an  impact  reaction  engine. 

A  portion  of  the  exhaust  gases  may  be  used  which  are  compressed  with  fresh  air 
through  the  fire  chamber.  This  is  desirable  in  some  cases,  so  as  not  to  get  such 
extremely  high  working  temperature,  the  proportion  of  air  and  burnt  gases  being 
settled  by  experiment  according  to  the  temperature  at  which  it  is  desired  to  work  as 
a  maximum. 

In  some  cases  which  are  worked  with  a  nearly  closed  cycle  the  gases  exhaust  from 
the  reaction  engine  at  a  pressure  of  several  atmospheres.  They  are  then,  by  preference, 
passed  through  a  re-generator  and  cooler,  after  which  they  are  pumped  through  the 
re-generator  and  the  fire  chamber  together  with  the  necessary  amount  of  fresh  air  to 
support  combustion. 

In  another  form  the  fire  chamber  burning  solid  fuel  is  replaced  by  a  chamber  into 
which  powdered  coal  or  oil  is  injected  together  with  the  air  for  the  purpose  of  com- 
bustion,  and  to  act  as  a  work- 
ing fluid ;  the  chamber  is  kept 

under    a    high    pressure,    com-  //2^T~  'h 

bustion  taking  place  immedi- 
ately and  completely,  the  pro- 
ducts issuing  at  a  high  velocity 


FIG.  227. — Ferranti's  Hot  Gas  Turbine. 

through  expansion  tubes  and  then  giving  up  their  energy  to  the  impact  engine.  In 
this  case  a  portion  of  the  products  of  combustion  may  also  be  introduced  with  or 
without  cooling,  and  with  or  without  a  regenerator  into  the  fire  chamber.  Coal  or 
other  gas  may  be  used  for  compression,  and  injected  in  place  of  the  other  combustible 
into  the  fire  chamber  together  with  the  same  or  other  modifications  in  the  cycle  above 
described. 

In  some  cases  the  high  speed  reaction  engines  are  combined  with  the  necessary 
pump  gear  driven  for  compressing  the  working  fluid  through  the  fire  chambers.  The 
gearing  is  so  arranged  that  the  high  speed  of  rotation  of  the  motor  is  geared  down  to 
a  sufficiently  slow  speed  to  work  the  reciprocating  compressors. 

When  air  and  the  products  of  combustion  are  used  as  a  working  fluid,  the  speed 
and  power  are  regulated  by  the  amount  of  the  fluid  which  is  compressed  through 
the  fire  chamber,  the  pressure  being  kept  constant,  or  as  nearly  so  as  possible,  by 
bringing  more  or  less  expansion  tubes  into  play  to  act  upon  the  wheel,  the  object  of 
this  being  to  always  work  with  the  maximum  range  of  temperature  and  so  secure  the 
maximum  economy  at  low  loads. 

When  working  with  steam  condensing   impact   engines  or  turbines,  ejector  con- 


Gas  Combustion  Turbines 


191 


densers  are  used,  in  which  the  necessary  power  required  outside  the  engine  con- 
tained in  the  steam  is  supplied  by  means  of  a  high  pressure  jet  of  water  generated 
by  a  high  speed  centrifugal  pump  run  direct  by  the  axis  of  the  reaction  engine 
which  supplies  a  small  jet  of  water  which  acts 
by  induction  on  a  larger  jet  of  water  in  the 
condenser. 

In  some  cases  a  water  spray  or  cooling 
jackets  may  be  used  in  the  air  compressors,  but 
where  such  is  the  case  it  is  desirable  so  far  as 
possible  to  separate  the  moisture  so  that  it  should 
not  pass  into  the  combustion  chamber. 

Fig.  227  shows  a  combination  of  hot  air  fur- 
nace, compressing  pumps,  and  reaction  engine  ; 
and  a  fire  chamber  arranged  for  burning  gas,  oil, 
or  other  suitable  fuel  is  shown  in  the  left-hand 
Figure. 

At  Fig.  227  (z)  is  a  hot  air  chamber,  (/)  is 
an  entrance  for  compressed  air,  (k)  is  an  arrange- 
ment for  introducing  the  fuel,  (/)  is  the  exhaust 
for  the  burnt  and  heated  gases  to  the  reaction 
engine  (m),  (n)  is  an  air  compressor. 

The  air  pump  is  shown  driven  by  a  worm 
and  wheel  gear. 

None  of  these  proposals  are  practicable.  It 
will  be  observed  that  the  working  pressure  can 
never  exceed  the  pumped  air  pressure  ;  it  is  the 
volume  of  the  gases  which  are  increased  by  the 
heat.  The  same  proposals  were  made  half  a 
century  ago  for  reciprocating  piston  engines  by 
Joule.  The  fluid  is  taken  in  at  one  volume 
and  rejected  at  a  larger  volume,  but  the  ex- 
pansion takes  place  mostly  in  the  furnace,  and 
the  power  is  proportional  to  the  difference  in 
area  between  the  pump  piston  and  the  engine 
piston. 

The  most  successful  engine  of  this  type 
working  on  the  reciprocating  principle  is  that 
known  as  the  Bucket  Engine,  described  in  Vol. 
II.  of  this  work.  I  have  worked  upon  the  idea 
of  the  internal  combustion  turbine  or  hot  gas 
turbine  myself  for  some  years,  and  my  own  con- 
clusion on  the  matter  is  that  the  combustion 
must  not  be  continuous  ;  and  the  engine  must  be 
worked  by  a  fluid  which  is  taken  into  the  com- 
bustion chamber  at  one  pressure,  and  sent  out  at  a 
higher  pressure  to  expand  in  the  turbine.  Experi- 
ments led  to  the  adoption  of  a  pressure  generator, 
as  shown  in  Fig.  228,  which  is  a  diagram  drawn 
to  explain  the  invention,  without  regard  to  details 
of  construction. 

It  consists  of  a  turbine  with  nozzles  as  usual, — a  combustion  chamber  into  which  the 
air  and  fuel  are  forced  or  drawn,  an  ignition  plug  to  fire  the  mixture.  In  the  diagram 
the  air  and  oil  fuel  enter  the  combustion  chamber  by  one  valve,  and  pass  through  a  throat, 


192  Modern  Engines 


in  order  that  the  fresh  incoming  charge  should  clear  out  the  remains  of  the  previously 
fired  charge. 

The  air  and  oil  may  be  drawn  in  by  a  suction  fan  on  the  turbine  exhaust  much 
as  they  are  drawn  into  a  motor  car  petrol  engine  cylinder,  but  it  is  preferable  to 
force  them  in  under  pressure.  A  compression  air  pump  and  reservoir  is  therefore 
provided,  and  the  air  used  at  from  50  to  80  Ibs.  pressure.  The  oil  reservoir  is  con- 
nected to  this  same  air  reservoir,  so  that  the  oil  and  air  are  at  equal  pressures  at  the 
admission  valve. 

The  action  of  the  apparatus  is  as  follows  : — 

The  reservoir  of  compressed  air  is  opened  by  the  check  valve.  Air  and  oil  enter 
by  the  admission  valve  to  the  combustion  chamber.  The  ignition  plug  is  sparking ; 
immediately  the  mixture  reaches  the  ignition  the  mixture  fires,  and  the  increase  of 
pressure  closes  the  admission  valve.  The  hot  gases  under  pressure  rush  through  the 
nozzle  and  drive  the  turbine.  As  soon  as  the  pressure  falls  below  that  of  the  air 
reservoir,  air  and  oil  again  automatically  enter  the  admission  valve,  driving  the  burnt 
gases  before  them  until  they  reach  the  sparking  plug,  when  another  combustion  occurs. 
The  valve  again  closes,  and  the  turbine  obtains  another  impulse,  and  so  on  the  cycle 
goes  intermittently. 

The  air  pump  is  driven  by  gearing  from  the  turbine,  and  the  half  of  the  combustion 
chamber  near  the  throat  is  cooled  by  water  jacket  The  nozzle  is  also  water  jacketed. 

In  some  cases  the  sparking  plug  has  been  tried  about  the  middle  of  the  chamber,  in 
order  to  present  an  elastic  gas  cushion  between  the  fired  gases  and  the  nozzle,  and  to 
prevent  flame  passing  through  the  nozzle. 

The  necessity  for  water  cooling,  of  course,  reduces  the  efficiency  much  in  the  same 
degree  as  in  the  reciprocating  engine,  although  in  the  turbine  a  higher  temperature  of 
the  working  fluid  is  permissible. 

The  continuous  combustion  generator  is  best  adapted  for  solid  fuel,  coal,  or  coke, 
while  the  intermittent  system  is  best  for  gaseous  or  liquid  fuel. 

THE   DESIGNING  OF  TURBINES 

No  detail  designs  for  steam  turbines  have  as  yet  been  published.  Patent  specifica- 
tions only  give  the  principles  and  methods,  and  generally  the  designs  are  as  far  from 
actual  practice  as  the  Patent  Law  will  allow.  Only  by  actual  dissection  of  working 
turbines  can  the  actual  construction  be  found.  For  the  benefit  of  engineers  who  may 
desire  to  have  a  more  intimate  acquaintance  with  turbines'  design  and  construction, 
I  shall  here  conclude  this  chapter  by  a  design  which  has  been  made  and  tried  by 
myself.  There  are  many  who  may  find  a  use  for  small  steam  turbines,  easily  and  cheaply 
made,  not  of  transcendental  economy  in  steam,  but  as  good  as  small  steam  engines 
reciprocating,  and  of  same  output  of  power. 

Two  types  of  turbines  were  chosen  :  first,  the  Pilbrow  double  wheel  type,  described 
in  his  Specification  No.  9568  of  year  1843,  and  shown  in  diagram  Fig.  163,  the  two 
wheels  running  in  opposite  direction  and  coupled  by  gearing. 

The  Seger  steam  turbine,  illustrated  in  Fig.  210  (p.  169),  is  of  this  type,  the  gearing 
being  belting. 

The  proper  form  of  the  passages  in  the  two  wheels  is  shown  in  the  diagram  Fig.  162. 
The  steam  enters  from  nozzles  converging  on  the  first  wheel,  into  which  it  flows  at  a 
pressure  about  10  to  15  per  cent,  less  than  that  due  to  the  boiler,  with  a  velocity  of  about 
1500  feet  per  second.  It  thus  drives  the  first  wheel  by  impact  and  pressure.  It  expands 
in  passing  the  first  wheel,  and  acquires  more  velocity  up  to  about  2000  feet  per  second. 
It  then  enters  the  second  wheel,  and  by  impact  drives  that  wheel  in  the  opposite  direction. 
Many  attempts  have  been  made  to  carry  this  action  further,  with  a  view  to  reducing  the 
speed  of  the  wheels,  by  adding  more  wheels  in  series,  but  such  a  practice  is  fallacious. 


Steam  Turbine   Design 


193 


With  these  partial  flow  wheels  two  wheels  only  give  the  maximum  results.  All  other 
arrangements  are  contrary  to  theory,  and  obviously  bad.  If  we  want  slower  velocities 
to  deal  with,  then  the  second  type  of  turbine,  herein  described,  must  be  adopted,  that 
described  by  Wilson  in  his  Specification,  No.  12,060  of  year  1848,  and  perfected  by  the 
Hon.  C.  A.  Parsons,  and  now  well  known. 

There  is  no  getting  away  from  the  fact  that  either  one  or  the  other  type  is  the  only 
choice  for  simple  construction  and  good  performance. 

If  we  attempt  to  put  up,  say,  a  series  of  De  Laval  wheels  we  meet  with  immense 
mechanical  difficulties,  not  to  speak  of  steam  distribution  difficulties.  In  large  size 
turbines  these  difficulties,  by  high-class  tools  and  workmanship  and  fine  designing, 
can  be  and  have  been  overcome  to  a  large  extent  in  machines  over  100  horse-power. 
Engineers  who  make  turbines  over  100  horse-power  can  generally  get  all  the  designs 

400 


350 


300 


250 


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f 

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C 

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y 

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t 

5 

10  15          20           25  30          35 

FIG.  229.  —  Turbine  Speed  Curve. 


40 


45 


50 


they  require  from  a  highly  trained  and  paid  staff.  The  designs  now  under  consideration 
are  intended  as  instructive  and  useful  to  those  who  may  have  to  make  their  own  designs 
and  work  out  smaller  affairs. 

Taking  the  first  design,  the  two  wheels  are  our  first  concern.  We  shall  assume 
a  turbine  is  required  for  5  horse-power,  steam  pressure  100  Ibs.  at  the  boiler,  non- 
condensing.  It  will  give  much  more  power  condensing,  and  may  so  be  used  by 
arranging  a  proper  packing  for  the  shafts,  to  prevent  air  being  drawn  in. 

In  this  class  of  turbine,  with  a  single  wheel,  a  peripheral  speed  on  the  middle 
diameter  of  the  buckets  is  less  the  smaller  the  turbine  is,  owing  to  the  weakness  of 
smaller  wheels  in  comparison  with  larger  ones.  Thus  a  De  Laval  5  horse-power  wheel 
is  made  for  515  feet  peripheral  speed  per  second,  while  the  300  horse-power  machine 
runs  at  1378  feet. 

The  revolutions  in  the  first  case  are  30,000,  and  in  the  latter  10,600  per  minute. 

As  the  turbine  under  discussion  has  two  wheels,  each  to  run  at  half  the  velocity  of  a 
single  wheel,  I  have  therefore,  from  the  published  results  of  the  De  Laval  wheels  and  their 
VOL.  i.  —  13 


Modern   Engines 


speeds,  which  have  been  found  in  practice  satisfactory,  made  a  curve  for  double  wheels 
(Fig.  229)  which  shows  the  relation  between  horse-power  and  peripheral  speeds  at  half 
the  revolutions  of  a  single  wheel,  the  5  horse-power  machine  having  a  speed  for  each 
wheel  equal  to  250  per  second. 


TABLE  XXV.— TABLE   SHOWING  VELOCITIES  AND   HORSE-POWER   OF  TURBINE 
WHEELS— NON-CONDENSING.     ( Theoretical. ) 


Initial 
Steam 
Pressure, 
Lbs.  per 
Square 
Inch. 

Counter-Pressure,  I  Atmosphere. 

Initial 
Steam 
Pressure, 
Lbs.  per 
Square 
Inch. 

Counter-Pressure,  I  Atmosphere. 

Velocity  of 
Outflow  of 
Steam, 
Feet  per 
Second. 

Kinetic 
Energy, 
Foot-lbs. 
per  Second. 

Horse-power 
of  550 
Foot-lbs. 
per  Second. 

Velocity  of 
Outflow  of 
Steam, 
Feet  per 
Second. 

Kinetic 
Energy, 
Foot-lbs. 
per  Second. 

Horse-power 
of  550 
Foot-lbs. 
per  Second. 

Per  Lb.  of  Steam  per  Hour. 

Per  Lb.  of  Steam  per  Hour. 

60 

2421 

25.29 

0.046 

160 

2992 

38.63 

0.070 

80 

2595 

29.06 

0.053 

1  80 

3058 

40.35 

0.073 

IOO 

2717 

31.86 

0.058 

200 

3"5 

41.87 

0.076 

1  20 

2822 

34-37 

0.062 

220 

3166 

43.26 

0.079 

140 

2913 

36.62 

0.066 

280 

3294 

46.83 

0.085 

There  being  two  wheels  running  in  opposite  directions  at  half-speed,  250  each,  we 
may  calculate  the  steam  required  at  the  same  rate  as  for  one  wheel  going  at  500  revolu- 
tions per  second,  the  object  of  the  two  wheels  being  to  reduce  speed  only. 

From  Table  XXV.  we  find  that  with  100  Ibs.  pressure  and  the  theoretical  velocity 
2717  per  second  the  horse-power  is  0.058  per  Ib.  of  steam,  so  that  if  the  turbine  is  to  be 

5 


5  horse-power  the  consumpt  of  steam  would  be 


0.058 


=  86  Ibs.  per  hour. 


But  we  cannot  run  wheels  at  such  high  speeds  in  practice.  The  strength  of  material 
limits  the  speeds,  and  the  5  horse-power  wheel  comes  out  at  4  inches  diameter  at  the 
mid-line  of  the  buckets.  The  peripheral  speeds  are  given  in  the  curve  (Fig.  229)  up 
to  50  horse-power,  and  these  speeds  multiplied  by  a  constant,  which  appears  to  be  2, 
gives  the  maximum  revolutions  of  a  single  wheel.  This  constant  will  then  be  equal 
to  i  for  double  wheels  at  maximum  speed. 

The  steam  required  is  inversely  proportional  to  the  peripheral  velocity  ;  hence  we 
have  found  that,  as  86  Ibs.  per  hour  are  required  at  the  high  theoretical  speed,  we  can 
find  what  is  necessary  at  the  lower  practical  speed,  500.  We  will  reduce  the  steam 

o/r 

consumption  to  Ibs.  per  second,  — — =.024;    then   500  :  2717  ::  .024  =  0.1304   Ibs.   per 

3600 

second,  472  Ibs.  per  hour. 

We  have  seen  that  the  flow  ot  steam  at  its  maximum  is  Q  =  37o  AD  in  Ibs.  per 

Q 


minute,  where  A  is  the  area  of  the  nozzle  at  the  narrow  end  ;  hence 

8 


=  A. 


Q  in  this  case  equals  8  nearly,  therefore 

8 


100  Ibs.   pressure  =  0.23.     Therefore 


370x0.23 


370  x  D 

-^p:  =  A,  and  D  the  density  of  steam  at 
370  D 

=  0.09  square  inch,  equal  to  one  jet  of 


•  c 

—  inch  diameter,  or  two  jets  each  of  about  —  inch. 
32  32 


Double  Wheel  Turbine 


'95 


The  quantity  of  steam  seems  large,  but  for  a  small  non-condensing  engine  at 
100  Ibs.  boiler  pressure  it  is  by  no  means  uncommon.  The  turbine  gains  more  by 
condensing  than  a  reciprocating  engine,  so  that  probably  half  the  steam  would  be  saved 
by  condensing. 


The  jets  would  be  reduced  in  area  by  one-half  for  condensing,  as  may  be  gathered 
from  the  following  table,  in  which  it  will  be  seen  that  the  horse-power  is  doubled  at 
100  Ibs.  pressure,  exhausting  into  a  28-inch  vacuum: — 


196 


Modern   Engines 


TABLE  XXVI.— TABLE  OF  VELOCITIES  HORSE-POWER  EXHAUSTING  INTO  VACUUM. 


Steam 
Pressure, 
Lbs.  per 
Square 
Inch. 

Counter-Pressure  0.93  Lbs.  per  Square 
Inch  absolute,  corresponding  to 
28-inch  Vacuum. 

Steam 
Pressure, 
Lbs.  per 
Square 
Inch. 

Counter-  Pressure  0.93  Lbs.  per  Square 
Inch  absolute,  corresponding  to 
28-inch  Vacuum. 

Velocity 
of  Outflow 
of  Steam, 
Feet  per 
Second. 

Kinetic 
Energy, 
Foot-lbs. 
per  Second. 

Horse-power 
of  55° 
Foot-lbs. 
per  Second. 

Velocity 
of  Outflow 
of  Steam, 
Feet  per 
Second. 

Kinetic 
Energy, 
Foot-lbs. 
per  Second. 

Horse-power 
of  550 
Foot-lbs. 
per  Second. 

Per  Lb.  of  Steam  per  Hour. 

Per  Lb.  of  Steam  per  Hour. 

60 

3680 

58.44 

o.  106 

160 

4°45 

70.61 

0.128 

80 

3793 

62.08 

0.113 

180 

4091 

72.22 

0.131 

IOO 

3871 

64.66 

0.118 

200 

4127 

73-50 

0.134 

120 

3940 

66.99 

0.  122 

220 

4159 

74.64 

0.136 

T4O 

3999 

69.01 

0.125 

280 

4229 

77.18 

0.140 

We  have  now  seen  that  the  wheels'  diameter  must  be  calculated  at  the  velocities  as 
given  by  a  curve  (Fig.  229),  and  the  area  of  the  nozzles  is  calculated  from  the  steam 
required  per  second ;  and  having  found  these,  the  design  becomes  a  mechanical 
problem. 

This  double  wheel  turbine,  as  designed,  is  shown,  £  actual  size,  in  the  three  Figs. 
230,  231,  and  232. 

Fig.  230  is  a  sectional  plan,  showing  the  two  wheels  A  and  B  carried  on  flexible- 
ended  shafts  SS. 

Fig.  231  is  a  side  elevation,  showing  the  base,  the  wheel  gearing,  and  governor. 

Fig.  232  is  an  end  view,  showing  gearing  wheels,  governor,  and  regulating  wheel 
for  cutting  off  nozzles,  and  governor  driving  band. 

Referring  to  Fig.  230,  the  special  features  are  the  gearing,  consisting  of  an  external 
and  internal  cut  toothed  wheel  E  and  I.  By  this  device  the  two  turbine  wheels  are  geared 
to  one  counter-shaft,  and  their  speed  reduced  and  power  added. 

If  the  large  wheels  are  made  of  raw  hide  leather,  compressed  into  gun- metal 
shrouds,  the  wheels  are  both  silent  and  durable.  The  wheels  are  made  heavy  in 
order  to  act  as  buffer  fly-wheels,  so  that  in  the  event  of  a  sudden  heavy  load  being 
applied,  such  as  a  short  circuit  on  a  dynamo  driven  by  the  machine,  the  inertia  of 
the  wheels  would  absorb  the  shock  before  it  could  be  transmitted  to  the  thin  flexible 
shafts  SS. 

The  metallic  packing  at  the  bearings  PP  is  specially  designed  to  work  tight,  either 
on  pressure  or  vacuum.  Rings  on  the  shaft  made  of  anti-friction  metal  slip  thereon.  A 
good  fit  between  these  rings  are  cast  iron  or  steel  spring  rings,  which  fit  the  bore 
closely  ;  a  spiral  spring  keeps  the  rings  in  contact  sideways.  These  packings  are 
lubricated  by  gravity  feed.  In  the  practical  design  of  larger  engines,  bearings  are 
placed  beyond  these  packed  bearings  to  take  the  strains  up. 

The  nozzles  are  bored  in  the  body  of  the  casing,  and  regulated  by  a  cover  ring 
sliding  over  them,  and  which  is  moved  by  hand  wheel  W  and  a  rack  and  pinion,  shown 
in  Fig.  233. 

In  Fig.  231  the  counter-shaft  C  is  seen  passing  through  the  base,  as  also  is  the 
governor  G  fixed  to  the  stop  valve  V  and  driven  by  belt. 

This  governor  can  be  also  driven  by  direct  connection  to  the  shaft  C,  and  the  valve 


Double  Wheel  Design 


197 


operated  by  a  simple  lever.     The  exhaust  is  connected  to  the  end  cover,  preferably  at 
the  bottom. 


(/) 


The  turbines  work  extremely  well,  and  without  attendance  of  any  special  kind. 


Modern   Engines 


Recently  an  improved  system  of  forming-  buckets  on  the  wheels  has  simplified  the 
construction  (see  page  168). 

The  sliding  cover  ring  for  regulating  the  nozzles  is  shown  in  Fig.  234,  where  it  will 
be  seen  that  with  three  nozzles  the  cover  has  one  hole  same  size  as  nozzle  inlet,  another 
hole  twice  the  length,  and  another  thrice  the  length  of  the  first,  so  that  by  sliding  the 
ring  the  holes  may  be  closed  in  succession.  This  may  be  done  by  a  governor  and  relay 
in  larger  turbines. 

This  type  of  turbine  is  intended  for  powers  from  £  horse-power  to  50  horse-power. 

For  larger  powers  the  second  design  conies  in.  As  it  has  been  fully  described  in  the 
foregoing  pages,  under  the  description  of  Parsons'  turbines,  we  need  not  go  into  the  details. 


FIG.  232. — End  View  of  Double  Wheel  Turbine.     Scale,  £  actual  size. 

Theoretically,  the  difference  in  pressure  between  wheel  and  wheel  in  a  series  of 
wheels  should  be  very  small.  P  is  the  pressure  at  the  inlet  side,  and  Pl  the  pressure  at 
the  outlet  side. 

P!  should  be  considerably  greater  than  £  of  P.     The  maximum  flow  of  steam  is 

p 
obtained  when  ~l  =  0.577,  and  P1  =  0.577  x  P.     Consequently  if  we  had  a  nozzle  like  that 

shown  in   Fig.   108,   with  steam  at   100  Ibs.   pressure  entering  at  the  wide  end,    the 
pressure  at  B,  just  beyond  the  throat,  would  be  P:  =  0.577  x  100  =  57.7  lbs- 


Regulate  Slide  for  Turbine  199 

The  pressure  in  one  wheel  should,  in  fact,  differ  by  only  a  few  pounds  from  that  of 
the  next ;  the  quantity  of  the  steam  passed  will  then  be  Q=  1.75  k*J(p-p\)p\>  wherein 
Q  =  weight  of  steam  per  minute. 
A  =  area  of  passages  in  square  inches. 
p  =  absolute  pressure  inside  one  wheel. 
p^=       ,,  ,,  ,,        the  next  wheel. 

Thus  if  A  =  o.i  square  inch,  and  p=ioo,  and  ^  =  95  Ibs.  per  square  inch,  then 
Q  =  1.75  x  o.i  N/(IOO  -  95)95  =  3.7  Ibs.  per  minute,  or  a  quantity  Q?  of  16  cubic  feet 

of  steam.     From  this  the  velocity  can  be  found  in  feet  per  second  =  ^ 23— _ii 

60  x  A       60  x  o.  i 

=  384  feet  per  second,  from  which  it  will  be  at  once  seen  that  the  velocity  of  the  wheel 
can  be  brought  much  nearer  the  theoretical  at  not  a  very  great  velocity. 

But  this  small  drop  in  pressure  can  only  be  obtained  by  a  very  long  series  of  wheels, 
with  very  small  blades  and  close 
together  :  conditions  easily  enough 
met  in  large  turbines,  but  very  diffi- 
cult in  small  ones.  Hence  in  this 
class  of  turbine  it  is  not  advisable 
to  make  them  below  20  or  25  horse- 
power. 

The  chief  cause  of  their  ineffici- 
ency  in   small    sizes    is    due    to   the         FIG.  233.— Rack  and  Pinion  of  Double  Wheel  Turbine, 
clearance   spaces    required  for   free 

rotation  and  the  consequent  leakage  of  steam  past  the  blades.  The  clearance  is  much 
greater  in  proportion  to  the  blade  area  in  a  small  turbine  than  it  is  in  a  large  one. 

The  problem  is  to  design  a  wheel  with  blades  easily  made  and  with  very  many 
blades  of  thinnest  material  on  the  wheel,  the  blades  to  be  increased  in  area  by  increase 
of  radial  length,  and  to  be  very  narrow  axially. 

In  order  to  make  wheels  to  meet  the  requirements,  a  plain  disc  is  turned  up  true 

and  with  a  rim  (Figs.  208,  209). 
The  disc  is  slotted  out  all  around, 
forming  slots  into  which  the  blades 
are  firmly  driven  ;  these  blades  are, 
at  first,  plain  steel  stampings  ;  the 
upper  part  is  then  bent  into  shape. 
They  are  then  inserted  in  radial 

slots  in  the  wheels,  and  the  lower 
FIG.  2^4. — Nozzle  Regulator  of  Double  Wheel  Turbine.  . 

part    flattened    back    tangentially, 

thus  firmly  fixing  the  blades  ;  they  are  afterwards  further  fastened  by  rivets.  In  this 
way  a  light  strong  wheel  is  formed.  It  is  important  for  economy  of  steam  that  the 
wheels  should  be  narrow  and  the  blades  numerous  and  thin.  This  design  meets  these 
requirements. 


CHAPTER    IV 


ROTARY  PISTON  ENGINES 


THIS  class  of  engine  is  but  little  used  as  a  prime  mover.  It  is,  however,  used  to  some 
extent  as  a  reversed  motor  for  pumping"  water  and  blowing  air.  And  it  would  seem 
that,  even  in  these  humble  capacities,  it  is  to  be  superseded  by  the  free-running  centri- 
fugal or  screw  pumps  for  both  air  and  water.  However,  no  work  on  prime  movers  and 


FIG.  235. — Diagram  of  Rotary  Piston  Engine. 

modern  engines  would  be  complete  without  including  an  example  or  two  of  the  best 
of  the  class  and  latest  developments  in  their  construction. 

Perhaps  more  brains  and  money  have  been  spent  on  the  invention  of  such  engines 
than   on   steam   turbines,    and   yet   they   have   never    reached   any   practicable   design 

200 


Rotary   Piston  Engines  201 

approaching  that  of  the  turbine.  Most  middle-aged  engineers  can  recall  to  mind  many 
brave  attempts  to  run  rotary  engines  successfully,  all  introduced  with  high  hopes  and 
determination  to  succeed,  all  with  same  discouraging  end.  I  can  remember  in  my 
youth  two  vessels  fitted  out  with  rotary  engines  in  Scotland  by  a  determined  inventor, 
who  fully  believed  he  had  solved  the  difficulties.  They  both  sailed  away,  never 
again  to  be  heard  of:  an  impressive  fact,  which  forcibly  sent  home  the  lesson  that  no 
uncertain  experiments  should  be  made  on  sea-going  vessels. 

The  mistaken  idea  underlying  nearly  all  the  inventions  in  this  direction  seems  to 
be  that,  by  substituting  a  rotary  piston  for  a  reciprocating  piston,  the  to-and-fro 
motions  will  be  abolished,  and  therefore  only  smooth  regular  rotary  motion  obtained, 
with  all  the  advantages  of  such  a  regular  turning  movement.  But  if  one  turns  to  the 
patent  records  of  these  inventions  and  examines  them  all  carefully,  in  every  case 
wherever  an  engine  has  been  designed  at  all  capable  of  passable  working  for  a  time  it 
will  be  found  that  there  are  quite  as  many  reciprocating  parts,  to-and-fro  movements, 
as  in  a  simple  piston  and  crank  engine. 

It  will  also  be  found  that  the  pistons,  or  doors,  or  sliders  in  the  rotary  are  subjected  to 
great  rubbing  friction  at  high  speed,  causing  unequal  wear  and  tear  and  eventual  failure. 

One  diagram  (Fig.  235)  will  illustrate  the  whole  class.  A  is  a  shaft  running  through 
a  cylinder  C  and  supported  in  stuffing  boxes  in  the  cylinder  covers,  between  which 
covers  it  fits  steam-tight  without  end-play.  It  has  a  wing  B,  which  forms  the  rotary 
piston.  This  wing  must  fit  steam-tight  at  the  ends  and  at  the  periphery,  and  many 
ingenious  devices  have  been  devised  to  pack  this  piston  tight.  E  is  a  door  or  shutter, 
pivoted  at  F,  so  that  it  can  shut  up  into  D,  to  clear  the  piston  when  it  comes  round. 
G  is  .the  steam  inlet  and  H  the  exhaust  pipe.  Theoretically  this  looks  all  right,  and, 
beginning  with  this  simple  conception,  the  mechanical  inventor  adds  improvements 
and  alterations  innumerable,  and  produces  an  engine  which  has  all  the  defects  of  the 
simple  affair  sketched,  only  toned  down  and  made  partially  tolerable. 

BROWN'S    ROTARY   ENGINE 

In  Fig.  235  the  wing  piston  is  shown  fixed  to  the  shaft,  but  it  may  be  hinged  to 
it,  so  that  the  steam  will  press  it  tight  at  the  periphery.  Some  inventors  make  the 
piston  oval  or  eccentric.  We  shall,  however,  only  consider  briefly  the  last  and  best 
attempt  on  a  practical  scale,  as  described  by  Professor  Jamieson.  Fig.  236  is  a  cross- 
section  and  sectional  plan  of  this  engine  made  with  double  doors.  The  following  is 
an  index  to  the  parts : — 

SB  =   Steam  branch.  PS  =    Packing  strips. 

SP  =        ,,       ports  and  passages.  SS  =   Spiral  springs. 

SV  =       ,,       valves.  S     =   Shaft. 

VS  =   Valve  spindles.  ED  =   Exhaust  door. 

C     =    Cylinder.  EP  =         ,,        ports. 

P     =    Piston.  EB  =         ,,        branch. 

The  steam  enters  by  steam  branch  SB  into  the  steam  passage  SP. 
This  steam  passage  thus  forms  a  steam  jacket  to  half  the  cylinder.  It  may  be 
arranged  so  as  to  form  also  a  "water  trap"  (with  a  return  "loop"  to  the  boiler),  so 
that  nothing  but  dry  steam  shall  enter  the  cylinder.  The  underneath  side  of  the 
cylinder  is  steam  jacketed  by  the  exhaust  steam.  The  outside  of  both  cylinder  covers 
and  jackets  are  carefully  lagged  with  felt,  and  covered  with  wood  to  prevent  radiation. 

The  steam  then  passes  through  the  steam  port  in  the  left-hand  revolving  steam 
valve  SV,  into  the  cylinder,  whenever  the  piston  P  has  passed  the  nose  of  the  left-hand 
oscillating  exhaust  door  ED.  The  piston  is  thereby  forced  round  under  full  steam 
pressure  until  it  reaches  the  point  of  "cut  off,"  when  the  left-hand  rotating  valve  closes 
the  steam  port.  For  the  remainder  of  the  stroke  the  piston  is  propelled  by  the  natural 


202 


Modern   Engines 


expansive  force  of  the  steam  (enclosed  between  it  and  this  steam  valve)  until  release 
takes  place  through  the  exhaust  port  EP,  in  the  boss  of  the  right-\\a.nd  exhaust  door  ED  ; 
from  whence  the  steam  passes  along  the  exhaust  passage  EP,  and  through  the  exhaust 
branch  EB,  to  the  atmosphere  or  to  a  condenser,  according  as  the  engine  is  working  as 
a  noncondensing  or  condensing  one.  Precisely  the  same  action  takes  place  during  the 
remaining  half  of  the  piston's  revolution  by  aid  of  the  n^A/-hand  steam  valve  and  the 
left-hand  exhaust  door. 

vs 


Cross  Section. 


Sectional  Plan. 
FIG.  236. — Brown's  Rotary  Engine. 

Nothing  could  be  simpler  under  the  circumstances,  or  more  effective ;  for  full 
advantage  is  taken  of  the  expansive  properties  of  steam  by  so  arranging  the  "lead"  of 
the  eccentric  (which  turns  the  steam  valves)  that  the  "cut  off"  may  take  place  at  any 
desired  proportion  of  the  piston's  stroke;  or  the  "cut  off"  may  be  directly  varied 
according  to  the  load  and  steam  pressure  by  connecting  a  loose  eccentric  to  the  governor. 

It  will  be  observed  that  the  front  edges  and  surfaces  of  the  exhaust  doors 
make  a  steam-tight  fit  with  the  circumferential  surface  of  the  piston,  and  that  when 
these  doors  are  closed  they  form  part  of  the  bore  of  the  cylinder.  They  are  forced 


Rotary  Piston   Engines 


203 


forward  by  the  incoming  steam  pressing  behind  them,  whenever  the  peculiarly  shaped 
piston  has  passed  them,  and  they  are  pushed  gently  back  into  their  seats  by  the  piston 
(during  expansion  and  release)  against  the  reaction  of  the  pent-up  or  "cushioning" 
steam  retained  between  them  and  the  steam  valves. 

The  working  surfaces  of  the  piston,  steam  valves,  and  exhaust  doors  are  all  packed 
by  gun-metal  strips,  kept  up  to  their  bearings  by  small  adjusted  spiral  springs.  From 
the  perspective  view  of  the  piston  (Fig.  237)  it  will  be  seen  that  the  side  and  end  packing 
strips  are  checked  into  each  other,  as  well  as  the  side  strips  into  the  ring  ones  next  the 
shaft.  In  order  to  make  the  wear 
uniform  on  the  side  packing  strips 
the  spiral  springs  are  made  propor- 
tionately shorter  the  farther  they  are 
from  the  centre  of  the  shaft ;  and, 
since  each  of  these  springs  are  con- 
tained in  the  same  length  of  hole, 
their  outward  pressure  on  their  strip 

is    inversely    proportional     to     their  FIG.  237.-Brown's  Piston, 

radial   distance    from    the   centre    of 
the  shaft ;   or,  in  other  words,  inversely  to  their  travel. 


BROWN'S  SINGLE-DOOR  ENGINE 

From  the  description  which  we  have  just  given  of  the  double-door  engine  the 
construction  and  action  of  the  single-door  one  will  be  easily  understood  from  Fig.  238. 
This  form  of  engine  has  not  been  steam  jacketed,  as  it  is  intended  for  rougher  and 
smaller  work  than  the  double-door  one,  such  as  driving  fans,  etc. 

The  points  claimed  for  the  engine  are  : — 

1.  Packing  strips  that  are  expected  to  wear  uniformly  and  last  a  long  time  without 
requiring  adjustment  or  renewal. 

2.  Early  cut  off  with  corresponding  economy,  due  to  taking  full  advantage  of  the 
natural  expansive  property  of  steam. 

3.  A  minimum  of  clearance  space. 

4.  Jacketing. 

5.  A  thoroughly  well  balanced  strong  engine,  occupying  a  minimum  of  space  for 

the  power  developed,  freedom  from  undue  vibra- 
tion and  noise,  combined  with  high  speed  and 
an  economy  of  steam  that  has  not  been  reached 
by  any  other  rotary  engine,  or  even  by  any 
simple  reciprocating  engine  of  the  non-conden- 
sing and  non-compound  type. 

6.  The  possibility  of  compounding  his 
engine,  or  even  of  adopting  triple  or  further 
multiple  expansion,  and  of  using  the  highest 
practicable  pressures. 

The  high  speed  of  the  rubbing  points  of  the 
doors,  and  that  under  great  pressure,  is  obvious, 


-PS 


FIG.  238. — Single-Door  Engine. 


even  in  this  otherwise  excellent  design,  but  the  number  of  reciprocating  parts  is  great, 
and  it  did  not  come  into  practical  use. 


THE   ROTA   ENGINE 

In  order  to  get  over  the  difficulty  of  this  high  speed  friction  between  the  piston  and 
cylinder  or  piston  and  doors  a  promising  idea  was  patented  by  Mr.  Macewan  Ross,  in 


204 


Modern   Engines 


which  the  cylinder  is  made  to  revolve  with  the  pistons,  so  that  their  relative  speeds 
are  much  reduced.  He  called  the  engine  the  "Rota"  engine.  Figs.  239  and  244 
represent  the  engine  in  sectional  elevation.  It  consists  of  a  cylindrical  casing  A  with 
closed  ends  or  covers,  through  whose  axis  from  either  end  pass  two  central  hollow 
drums  B  fixed  to  and  carried  by  their  respective  brackets  XX,  and  having  cast  in  them 
ports  for  admission  and  exhaust  of  steam  at  both  ends.  The  drums  B  (Fig.  244)  are 

A 


FIG.  239. — Section  of  Rota  Engine. 


divided  by  central  webs  running  their  entire  length  to  form  admission  and  exhaust 
passages  bb',  from  which  the  inlet  and  exhaust  ports  CC'  are  carried  to  the  interior  of  the 
casing.  A  series  of  segmental  pistons  EE  are  fitted  between  the  casing  A  and  drums  B, 
which  fill  up  to  a  greater  or  less  extent  what  forms  the  steam  space  within  the  casing. 

The  crank  shaft  D  (Figs.  239  and  240)  passes  through  bearings  bored  eccentrically 
in  the  drums,  and  is  made  with  four  arms  or  cranks  which  also  act  as  slides,  and  which 
are  fitted  into  slide  blocks  F  fitted  into  their  respective 
pistons.  The  pistons  are  thereby  held  in  equal  and  equi- 
distant angular  positions  relatively  with  the  axis  of  the 
main  casing  A  ;  the  slide  blocks  in  the  pistons  are  allowed 
to  oscillate  in  order  to  accommodate  themselves  to  the 
different  angular  positions  of  the  cranks,  which  recipro- 
cate radially  through  them  relatively  with  the  axis  of  the 
main  casing,  as  the  distance  of  the  piston  from  the  axis  of 
the  crank  shaft  varies  according  to  their  position  round 
the  drum  B.  Their  distance  apart  also  varies,  those 
pistons  bearing  on  the  portion  of  the  drums  having  least 
eccentricity  being  close  together,  and  those  on  the  opposite  side  being  farthest  apart. 
When  the  pistons  travel  round  the  drum  their  speed  is  highest  at  the  point  of  greatest 
eccentricity,  and  the  ports  CC'  are  formed  to  admit  steam  between  each  pair  of  pistons 
as  they  pass  the  point  of  least  eccentricity,  and  to  exhaust  as  they  pass  the  line  of 
greatest  eccentricity  of  the  drums.  The  steam  is  cut  off  at  any  desired  point,  and 


FIG.  240. 


Rotary  Piston   Engines 


205 


expands,  while  the  piston  in  front  of  it  is  impelled  forward  at  a  greater  velocity  than 
that  following  it.  The  intervening  space  increases  until  the  point  of  greatest  eccentricity 
is  reached,  when  the  exhaust  of  steam  between  that  pair  of  pistons  takes  place  through 

the  ports  C'  in  the  drums. 
Each  succeeding  piston  is  acted 
upon  in  like  manner,  and  a 
continuous  rotative  motion  is 
thus  imparted  to  the  crank 
shaft,  there  being  no  dead 
point,  and  all  parts  are  in 


FIG.  241. — Pistons  of  Rota  Engine. 


FIG.  242. — Casting  of  Pistons. 


perfect  equilibrium.  It  must  be  clearly  understood  that  the  drums  are  fixed  into  the 
brackets,  while  the  casing  is  in  no  way  connected  either  to  the  crank  shaft  or  to  the 
pistons,  but  is  free  to  rotate  upon  the  drums  and  accommodate  itself  to  the  friction 

within  the  engine.  Each 
cover  of  the  casing  has 
cast  upon  it  a  sleeve, 
which  is  carried  along 
around  the  drum  into 
a  staffing  box  in  the 
bracket,  and  those  sleeves 
form  the  bearings  upon 
which  the  casing  re- 
volves. The  sole  plate  is 
so  made  that  steam  enter- 
ing at  branch  pipe  S  (see 
Fig.  239),  to  which  the 
governor  is  fixed,  passes 
up  a  steam  way  formed  in 
bracket  X,  also  along  one 
side  of  the  sole  plate  to 
bracket  X',  and  so  is  ad- 
mitted into  the  interior  of 

FIG.  243—Rota  Engine  by  Macewan  Ross.  the  casinS  thr<>ugh  both 

drums  at  the  same  time. 

Similarly  the  exhaust  steam  passes  down  both  brackets,  and  exhausts  at  branch  T. 
It  will  be  seen  from  Fig.  241  that  the  steam  chamber  between  the  bottom  pair  of 
pistons  is  just  opening  to  steam,  and  the  chamber  at  the  top  is  opening  to  exhaust. 


2O6 


Hult  Rotary  Engine  207 

In  order  to  describe  more  clearly  the  cycle,  suppose  the  middle  of  a  side  chamber 
to  be  full  of  steam,  then  the  pressure  would  act  against  both  pistons  equally  ;  but 
you  will  observe  that  the  upper  crank  is  much  longer  than  the  lower  one,  so  that 
the  upper  crank  will  turn  in  an  upward  direction,  taking1  the  others  round  with 
it,  until  the  chamber  reaches  the  top  centre,  when  exhaust  will  take  place  through 
port  C' ;  and  meanwhile  the  bottom  chamber  will  be  round  to  half-stroke  and  getting 
full  steam,  so  that  there  are  always  two  cranks  doing  work  at  the  same  time,  and  thus 
there  is  no  dead  point.  The  pistons  therefore  act  as  their  own  valves  (the  ports  being  in 
the  fixed  drums),  so  that  the  chambers  only  take  what  steam  they  require,  and  leave  no 
passages  full  of  steam  after  cut  off  takes  place. 

There  is  a  steam  space  formed  in  the  outside  of  each  piston,  so  that  the 
accumulated  steam  pressure  acting  between  them  and  the  casing  is  made  almost  to 
balance  the  centrifugal  force  of  the  pistons.  It  must  also  be  noted  that  there  is  no 
side  pressure  on  the  pistons,  and  therefore  if  fitted  accurately  at  first  they  should  wear 
well. 

This  accuracy  is  easily  attained,  as  all  the  work  is  done  on  the  lathe,  the  pistons 
being  cast  all  together,  as  shown  on  Fig.  242,  with  distance  pieces  between  each,  and 
are  not  separated  until  they  have  been  turned  and  fitted  to  the  drum,  casing,  and  covers. 
Each  piston  and  crank  arm  is  fitted  with  suitable  springs,  those  in  the  cranks  being  so 
arranged  as  to  mutually  accommodate  themselves  should  there  be  any  end  movement 
of  the  shaft.  Let  us  now  consider  some  of  the  results  which  are  produced  when  the 
engine  is  working.  The  pistons,  which  are  close  together  when  in  the  bottom  position, 
are  3  inches  apart  when  at  the  top,  which  is  3  inches  travel  in  half  a  revolution,  or  a 
speed  of  6  inches  per  revolution. 

Now,  suppose  the  engine  to  be  running  at  its  normal  speed — 800  revolutions  per 
minute — the  relative  speed  of  piston  is  800  x  .5  feet  =  400  feet  per  minute,  and  as  there 
are  four  steam  spaces  we  have  a  total  "  outward  "  stroke  in  each  revolution  of  12  inches, 
and  yet  the  speed  of  piston  is  only  400  feet  per  minute. 

The  speeds  of  the  various  surfaces  working  in  contact  are  also  very  low,  as  will  be 
seen  from  the  adjoining  table  : — 

Pressures  on  Surfaces  Speeds  of  Surfaces 
working  in  contact,  in  working1  in  contact, 
Lbs.  per  Square  Inch.  in  Feet  per  Minute. 

Outside  of  pistons  and  casing        .              .  50  283 

Side  blocks  and  crank  arms           .              .  435  266 

Crank  shaft  journals           ...  78  366 

Casing  journals  on  drums ...  40  900 

Although  the  latter  speed,  namely,  the  bearings  of  the  casing,  seems  high,  still  it  is 
under  constant  pressure,  and  is  well  lubricated  from  holes  being  bored  through  into  the 
exhaust  passage  V  in  the  drum. 

The  novel  principle  in  this  engine  was  the  cylinder  revolving  with  the  pistons. 
Fig.  243  is  a  view  of  the  complete  engine  with  the  shaft  fitted  with  a  coupling. 


THE  HULT  ENGINE 

Starting  from  the  same  point  as  Macewan  Ross,  but  some  years  later,  this  inventor 
made  some  improvements  on  the  "Rota"  engine  type,  and  by  introducing  roller  and 
ball  bearings  reduced  the  friction. 

Starting  from  this  point,  the  inventors  of  the  Hult  engine  have  made  the  cylinder 
participate  in  the  rotary  motion  of  the  piston,  thus  substituting  rolling  friction  for  the 
sliding  friction,  which  had  shown  itself  fatal  to  efficiency  in  other  rotary  engines,  while 


208 


Modern   Engines 


they  are  thereby  enabled  to  readjust  the  contacts  between  the  piston  and  the  cylinder  ; 
these  advantages  belong-  to  no  other  system. 


PRINCIPLES  OF  THE  HULT  SYSTEM 

The  principles  of  the  Hult  engines  are  shown  in  the  schematic  Figs.  245  and  246. 
In  order  to  simplify  this  description  of  the  principles,  only  one  shutter  or  door  is  shown, 
instead  of  two  or  three  shutters  placed  at  respectively  180°  and  120°,  with  their  steam 
passages  for  each  shutter  ;  for  some  purposes  as  many  as  six  shutters  have  been  placed 
in  the  same  piston. 

The  piston  F,  placed  eccentrically  within  the  cylinder  C,  is  shrunk  on  the  main 
shaft  A,  and  is  provided  with  passages  for  the  admission  of  steam  H  and  for  the 
exhaust  I  ;  the  sliding  shutter  G  is  placed  near  the  admission  passage. 

The  steam  from  the  boiler  enters  through  the  hollow  shaft  A  and  the  passage  H 
into  the  space  enclosed  between  the  piston,  the  cylinder,  and  the  shutter,  and  pushes 


FIG.  245. — Single-Door  Hult  Engine. 

round  the  shutter  for  turning  the  piston,  the  shutter  having  the  same  length  as  the 
piston. 

When  the  piston  reaches  a  certain  angle  the  admission  of  steam  is  cut  off  auto- 
matically by  a  valve  placed  inside  or  at  one  end  of  the  hollow  shaft.  The  volume  of 
steam  introduced  then  works  by  expansion  upon  the  shutter  G,  until  the  pressure 
becomes  low  enough,  when  the  rotary  motion  of  the  piston,  eccentric  to  the  cylinder, 
uncovers  the  openings  for  the  exhaust  steam.  There  is  no  organ  for  admission  or 
exhaust  of  steam  in  the  cylinder  itself. 

Centrifugal  force  acting  upon  the  shutter  ensures  a  perfectly  steam-tight  fit  between 
the  shutter  in  the  piston  and  the  cylinder,  both  revolving  in  the  same  direction. 

The  shaft  with  the  piston  runs  on  the  roller  bearings  B,  K.  The  cylinder  runs  quite 
free  on  the  roller  bearings  E,  L  ;  it  is  drawn  round  by  the  piston  in  consequence  of  the 
pressure  between  them  at  the  line  of  contact.  The  piston  and  the  cylinder  have  thus 
the  same  circumferential  speed,  but  in  consequence  of  their  eccentricity  the  angular 
speed  of  the  piston  is  slightly  higher. 

In  the  Hult  engines  with  two  shutters,  placed  at  180°  to  one  another,  as  shown  in 
Figs.  247  and  248,  there  are  two  periods  of  steam  admission  during  each  revolution, 


Hult  Rotary   Engine 


209 


and  in  the  engines  with  three  shutters,  shown  in  Fig.  250,  there  are  three  such  periods. 
The  greater  number  of  shutters  increases  the  power  of  the  engine,  while  reducing  the 
condensation  within  the  cylinder. 

As  the  piston  and  the  cylinder  both  revolve  uninterruptedly  in  the  same  direction, 
the  piston  speed  can  be  conveniently  kept  up  to  50  or  60  feet  per  second,  or  about  twice 
the  speed  of  reciprocating  engines. 

The  cylinder  bearings  and  those  supporting  the  shaft  and  piston  are  all  roller 
bearings  with  tempered  steel  rollers,  kept  at  their  relative  distances  by  guide  rollers, 
as  shown  in  Fig.  246;  the  rollers  run  on  racers  fixed  in  the  frame  and  frame  covers 
respectively. 

When  easing  the  nuts  holding  the  frame  covers  the  adjusting  screws  on  the  top 


Bearings  of  Cylinder. 


Bearing's  of  Shaft. 


FIG.  246. — Roller  Bearings  of  Hult  Engine. 

of  the  frame  can  press  the  piston  and  the  cylinder  together  at  the  line  of  contact,  so 
as  to  ensure  that  the  cylinder  follows  the  rotation  of  the  piston,  while  keeping  the  line 
of  contact  steam-tight.  The  ends  of  the  piston  are  also  adjustable  in  relation  to  the 
cylinder,  as  described  farther  on. 

Referring  to  Figs.  247  and  248,  the  following  is  an  index  to  the  parts  : — 


Cylinder. 

Cylinder  end  on  governor  side. 

Cylinder  end  on  pulley  side. 

Adjustment  disc  for  piston  ends. 

Adjustment  wedges  for  piston  ends. 

Adjustment  screws  for  piston  ends. 

Piston. 

Sliding  shutters. 

!- Steam  admission  passages. 

Exhaust  passages. 
Exhaust  orifices  in  piston. 

VOL.  I. — 14 


13.  Main  shaft. 

14.  Frame. 

15.  Frame  cover  on  governor  side. 

16.  Frame  cover  on  pulley  side. 

17.  \Adjustment  screws  for  line  of  contact  between 

18.  )     piston  and  cylinder. 

19.  Cover  screw  for  reaching  adjustment  screws  6. 

2O*  ~\ 

'  |  Covers  for  shaft  roller  bearings. 

22.  Inner  racer  for  cylinder  roller  bearing. 

23.  Outer  racer  for  cylinder  roller  bearing. 

24.  Inner  racer  for  shaft  roller  bearing. 


Hult  Rotary   Engine 


21  I 


25.  Outer  racer  for  shaft  roller  bearing. 

26.  Steel  rollers  in  bearings. 

27.  Guide  rollers. 

28.  Hoop  for  cylinder  guide  rollers. 

29.  Hoop  for  shaft  guide  rollers. 

30.  Steam  admission  box. 

31.  Flange  for  admission  box. 

32.  Fixed  steam  distributing  tube. 

33.  Revolving  steam  distributing  tube. 

34.  Governor  valve. 

35.  Connecting-rod  between  revolving  distributing 

tube  and  admission  valve. 


36.  Revolving  steam  admission  valve. 

37.  Governor  box. 

38.  Governor  disc. 

39.  Governor  weights. 

40.  Governor  pivot. 

41.  Governor  lever  plate. 

42.  Governor  lever. 

43.  Rod  for  turning  automatic  lubricator. 

44.  Holding-down  bolts. 

45.  Cover  bolts. 

46.  Exhaust  pipe. 

47.  Coupling. 


THE  HULT  TWO-SHUTTER  ENGINE  (Fics.  247,  248,  AND  249) 

The  steam  from  the  boiler  enters  into  the  box  30,  passes  through  tube  32,  and 
reaches  the  cylinder  through  passages  9  and   10,  every  time  one  of  them  has  passed 
the     line    of    contact    be- 
tween  the   cylinder  i   and 
the  piston  7.     The   steam 
acts  on  the  sliding  shutter 
8,  at  first  with   full   pres- 
sure, until  the  moment  of 
the    cut-off,    and   then   by 
expansion. 

The  distributing  ar- 
rangement, placed  in  the 
hollow  main  shaft  13, 
consists  of  an  inner  fixed 
tube  32,  an  outer  revolv- 
ing tube  33,  and  a  rod 

35,  connecting  the  tube  33 
with   the    admission   valve 

36,  which  is  perforated  by 
a  number  of  slots,  through 
which  the  steam  can  enter 
into     the     fixed    tube    32. 
The   tube  33,  the   rod  35, 
and    the     valve     36    thus 
participate    in    the    rotary 
motion    of    the    piston    7. 
The   revolving   tube  33   is 
pierced  with  slots  opposite 
to  the  passages  9  and  10, 


u 


I 


FIG.  248. — Steam  Ports.     Double-Door  Section. 


so  that  steam  at  full  pres- 
sure is   admitted   into  the 
cylinder      through      these 
passages  every  time  any  of  the  slots  passes  the   corresponding   orifice   in  the   fixed 
tube  32. 

The  governor,  placed  in  the  box  37,  is  of  a  centrifugal  type  ;  its  disc  38,  fixed 
to  the  steam  admission  valve  36,  at  the  end  of  the  rod  35,  which  is  bevelled  so  as  to 
allow  steam  to  pass,  turns  at  the  same  speed  as  the  piston  7.  The  weights  39, 
equilibrated  by  a  spring  and  mounted  on  the  pivot  40  on  the  disc  38,  are  connected 
by  levers  42  with  the  plate  41  on  the  rod  of  the  governor  valve  34,  which  has  openings 


212 


Modern   Engines 


corresponding-  to  those  on  the  admission  valve  36.  The  weights  39,  when  separated 
by  centrifugal  force,  pull  at  the  levers  42,  and  give  to  the  governor  valve  34  an  addi- 
tional rotary  motion,  independent  of  that  of  the  admission  valve  36. 

The  expanded  steam  escapes  from  the  cylinder  through  the  passages  n  and  the 
orifices  12  on  the  end  faces  of  the  piston. 

In  consequence  of  the  eccentricity  of  the  piston  in  relation  to  the  cylinder  there  are 
open  spaces  inside  the  end  pieces  of  the  cylinder  to  allow  for  the  movement  of  the  shaft. 
As  the  position  of  the  transversal  surfaces  of  these  spaces  does  not  change  during  the 
rotation  of  the  engine,  the  escapement  periods  are  determined  by  the  shape  and  section 
of  the  orifices  12. 

The  exhaust  steam  then  spreads  throughout  the  interior  of  the  frame  14,  and  issues 
finally  through  the  exhaust  pipe  46  to  the  condenser,  or  into  the  outer  air. 

The  roller  bearings  for 
the  cylinder  consist  of  tem- 
pered steel  rollers  26,  run- 
ning- on  steel  racers  22, 
fitted  on  the  annular  parts 
2  and  3  of  the  two  cylinder 
ends.  The  distance  between 
the  rollers  is  kept  constant 
by  guide  rollers  27,  mounted 
on  pins  fixed  on  hoops  28. 
Two  other  steel  racers  23 
are  fitted  in  the  frame  14, 
outside  the  rollers  concen- 
trically to  the  inner  racers 
22. 

The  driving  shaft  13, 
carrying  the  piston  7,  is 
supported  by  other  similar 
bearings,  consisting  of  the 
rollers  26,  the  inner  racers 
24,  guide  rollers  27,  hoops 
29,  and  outer  racers  25. 

These  shaft  bearings, 
independent  of  the  cylinder 
bearings,  can  be  adjusted 
vertically  by  turning  the  adjustment  screws  17  and  18,  which  give  to  the  piston  7  the 
exact  pressure  against  the  cylinder  necessary  for  rotating  the  cylinder,  and  for  ensuring 
a  perfectly  steam-tight  fit  at  the  line  of  contact. 

A  disc  4  is  placed  at  the  left  end  of  the  piston  for  adjusting  a  suitable  steam-tight 
fit  between  the  ends  of  the  piston  and  the  cylinder  ;  the  position  of  this  disc  is  modified 
by  the  adjustment  screws  6  pressing-  upon  the  wedges  5,  which  screws  are  reached  by 
a  screwdriver  on  removing  the  cover  screw  19. 

Whatever  slight  friction  there  may  be  at  the  ends  of  the  piston  is  almost  inappreci- 
able, as  the  cylinder  rolls  freely  in  the  same  direction  as  the  piston,  and  with  but  slight 
difference  in  the  angular  speed,  while  their  circumferential  speed  is  the  same. 

The  question  of  lubrication  is  important  for  all  high  speed  engines.  The  Hult 
engine  is  easily  lubricated,  because  rolling  friction  is  almost  entirely  substituted  for 
the  sliding  friction  existing  in  all  reciprocating  engines  ;  the  steam  on  entering  the 
engine  takes  up  the  exact  quantity  of  lubricating  oil  required  from  one  single  automatic 
lubricator  driven  by  the  rod  43,  set  in  motion  by  an  eccentric  cam  on  one  of  the 
hoops  29. 


FlG.  249. — Steam  Ports. 


Hult  Rotary  Marine   Engine  2,13 

THE  HULT  THREE-SHUTTER  ENGINE  (Fio.  250) 

This  is  in  most  respects  similar  to  the  two-shutter  engine,  except  that  there  are 
three  shutters,  with  three  admissions  of  steam,  and  the  cycle  of  admission,  expansion, 
and  expulsion  of  steam  for  each  shutter  is  completed  during  one  revolution  of  the  shaft. 

When  a  three-shutter  piston  with  its  arrangements  for  admission  of  steam  is 
substituted  for  a  two-shutter  piston  in  the  same  engine  the  power  is  increased,  and 
it  becomes  perhaps  even  better  equilibrated  than  before  ;  while  the  condensation  of 
steam  in  the  cylinder  be- 
comes, if  possible,  even 
less  detrimental. 

When  the  exhaust  com- 
mences of  the  steam,  which 
has  acted  upon  one  of  the 
shutters,  the  next  shutter 
is  driven  by  expanding 
steam,  and  the  third 
shutter  by  steam  at  full 
pressure  ;  while  immedi- 
ately afterwards,  and  be- 
fore the  said  exhaust  is 
completed,  fresh  steam  is 
again  let  on  to  the  first 
shutter. 

Fig.  250  shows  in  trans- 
verse section  the  steam 
admission  arrangement  of 
a  three-shutter  engine,  of 
the  same  size  as  that  of 
which  a  longitudinal  sec- 
tion is  given  in  Fig.  247. 

The  three  shutters  are 
marked  8,  the  three  admis- 
sion passages  10,  and  the 
three  exhaust  passages  1 1 ; 
the  steam  admitted  for  one 
shutter  through  the  pas-  FIG.  250. — Three-Door  Hult  Engine, 

sage     IOA    acts     upon    the 

shutter  SA,  and  is  exhausted  through  the  passage  IIA;  and  in  the  same  manner  IOB, 
SB,  and  IIB,  as  well  as  ice,  8c,  and  nc,  co-operate  together. 


THE  HULT  REVERSIBLE  ENGINE  FOR  MARINE  PURPOSES,  AUTO- 
MOBILES, ETC. 

Fig.  251,  representing  on  one-tenth  scale  a  Hult  marine  engine  giving  45  brake 
horse-power  at  10  atmospheres  pressure,  shows  its  convenient  form ;  the  200  brake 
horse-power  occupies  over  all  a  space  6  feet  long,  4  feet  high,  and  3  feet  wide.  The 
weight  of  the  marine  engines  generally  vary  from  30  Ibs.  to  45  Ibs.  per  brake  horse- 
power, according  to  power  and  steam  pressure. 

Engines  for  these  purposes  must  be  light  and  occupy  small  space  ;  they  must  be 
simple  in  construction,  easy  to  manage,  and  handy,  so  that  all  changes  of  speed  and 
direction  can  be  executed  easily  and  quickly. 

In    spite   of   all    recent   improvements,    reciprocating   engines   do   not   fulfil   these 


Modern   Engines 


conditions  as  perfectly  as  Hult  engines,  which  work  directly  on  the  screw  shaft  with 
higher  speed  than  can  be  obtained  with  reciprocating  engines,  while  their  small  dimen- 
sions are  in  every  way  convenient. 

Being  free  from  shocks  and  vibration,  they  can  be  mounted  in  ships  and  boats  of 
light  construction  ;  as  the  engine  shaft  is  coupled  in  direct  prolongation  of  the  screw 
shaft,  without  cranks  or  fly-wheel,  their  centre  of  gravity  can  be  placed  much  lower  than 
with  reciprocating  engines. 

The  description  given  above  of  stationary  Hult  engines  also  applies  to  the  marine 
engines,  except  in  the  arrangements  for  the  distribution  of  steam,  which  in  the  latter 
are  modified  to  suit  the  requirements  for  reversion  of  direction  and  variation  of  speed. 

The  reversion  is  obtained  by  moving  lengthwise  the  distributing  tube  for  admitting 
the  steam  on  one  side  or  the  other  of  the  sliding  shutters. 

Fig.  251  is  a  section  of  the  Hult  marine  engine  in  the  position  of  driving  "forward" 
at  full  speed.  The  distributing  tube  C,  which  does  not  participate  in  the  rotary  motion 
of  the  main  shaft  A,  is  moved  lengthwise  by  a  lever  D,  connected  by  a  rod  E  with  a  fixed 
point  P  on  the  frame. 

The  steam  introduced  from  the  boiler  into  the  box  F  passes  through  the  orifices  G 
into  the  distributing  tube  C,  pierced  by  the  slots  H,  which  by  the  longitudinal  movement 
of  the  tube  can  be  brought  in  line  with  one  or  the  other  of  the  steam  passages  M  and  N, 
as  required  for  the  desired  direction  of  rotation. 

As  the  tube  C  is  closed  at  one  end  by  the  stop  I,  the  steam  can  only  reach  the 
cylinder  through  the  slots  H  ;  the  exhaust  steam  escapes  through  the  orifices  K  or  L. 

In  the  position  shown  in  Fig.  251  the  slot  H  opens  fully  into  the  steam  passage  M, 
admitting  steam  for  driving  "forward";  the  exhaust  steam  passes  through  the  steam 
passage  N  and  (as  soon  as  this  passage  reaches  the  orifice  K)  into  the  space  outside 
stop  I,  in  the  distributing  tube  ;  it  then  passes  through  O  into  the  space  outside  the 
cylinder,  and  finally  to  the  exhaust  pipe  R. 

When  the  lever  D  is  set  for  "back,"  the  slots  H  come  opposite  the  steam  passage 
N  for  admission  of  steam  ;  the  other  passage  M  serving  in  this  case  for  the  exhaust 
each  time  it  opens  into  the  orifice  L,  cut  in  the  distributing  tube,  which  is  there  flattened 
out  for  the  passage  of  the  exhaust  steam. 

This  single  lever  thus  ensures  the  perfect  reversibility  of  the  engine  at  all  positions 
of  the  piston,  and  the  variation  of  speed  depends  upon  how  far  the  lever  D  is  moved 
from  its  central  "stop  "  position  in  the  direction  of  the  "  forward  "or  "  back  "  positions. 

The  following  table  gives  the  approximate  power,  speed,  and  weight  of  the  three- 
shutter  engines,  as  well  as  their  consumption  of  dry  steam  per  brake  horse-power  with 
exhaust  into  open  air. 

TABLE  XXVII. 


142  Lbs.  Pressure. 

Brake 
Horse-Power. 

Consumption  of  Steam 
per  Brake  Horse-power 
and  Hour,  with  Ex- 

Number of 
Revolutions 
per  Minute. 

Weight  of 
Complete  Engine. 

haust  into  Open  Air. 

Lbs. 

Cwt. 

8 

1500 

ii 

12 

36 

1300 

4* 

2O 

33 

1250 

6 

40 

31 

IOOO 

12 

DO 

29i 

850 

17* 

80 

28 

700 

23 

1  2O 

27i 

55° 

38 

20O 

27 

500 

,52 

Sectional  View. 


Complete  View. 
FlG.  251. — Hult  Rotary  Marine  Engine. 


215 


2 1 6  Modern  Engines 

The  above  figures  of  consumption  of  steam  without  vacuum  are,  of  course,  reduced 
when  working  with  condensation,  with  the  usual  ratio  of  gain  depending  upon  the 
vacuum  given  by  different  types  of  condensers. 

In  comparing  these  figures  with  those  of  other  engines  it  must  not  be  overlooked 
that  the  figures  here  given  are  for  brake  horse-power  ;  if  stated  for  indicated  horse- 
power, as  is  sometimes  done,  the  figures  would  be  proportionately  lower. 

This  chapter  shows  the  best  that  has  hitherto  been  done  in  the  direction  of  the 
Rotary  Piston  Engine.  It  may  be  observed  that  one  objection  still  remains,  and  that  is 
the  heavy  strains  in  other  directions  than  that  upon  the  shutter,  and  not  in  the  direction 
of  motion.  The  push  is  not  direct  in  the  line  of  motion,  but  constrained  into  that  line  by 
the  cylinder. 


Printed  by  MORRISON  &  GIBB  LIMITED,  Edinburgh. 


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UCD  LIBRARY 

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